They came heavily armed and utterly determined. Weighed down by automatic weapons and bags of gear, the men who brought chaos and horror to the streets of Mumbai apparently started their mission in black and yellow rubber dinghies.

The 20-somethings disembarked near the Gateway of India monument on Wednesday evening and began to fan out across the city, embarking on their rampage and showing no mercy to anyone who crossed their path.

Over at the iconic Taj Mahal hotel, a regular haunt of India's elite and wealthy tourists, the evening was in full swing. Patrons at the hotel, with its dome silhouette and imposing red, white and grey-brick façade, sweeping staircases, onyx columns and chandelier-laden ceilings, had little idea of the carnage coming their way. Some were tucking into a first-class curry in one of Mumbai's top eateries, while others gathered around the pool to discuss important business matters.

Dalbir Bains, a lingerie shop owner who moved from Britain to Mumbai three years ago, was finishing just such a meeting about 9.45pm when gunmen, described by some as "young boys" dressed in black shirts and jeans, stormed into the seafront hotel and opened fire indiscriminately.

"To begin with, we thought it might be fireworks or wedding celebrations but very quickly people started running towards us," Ms Bains recounted.

"We went into the main lobby and there was a man who had been shot in the leg. He was screaming 'help me, please'. It was only then that we truly realised we were under attack."

Separated from her friends, she was ushered into a first-floor room by staff, "They were incredibly calm, they locked the doors and turned off the lights, then put furniture – chairs, desks, whatever they could find – against the door".

Little did the Taj Mahal patrons realise the attack on their hotel was anything but an isolated incident.

By 11.10pm, Indian media began broadcasting details of a large-scale shooting at the city's Chhatrapati Shivaji Terminus train station. The assailants were also young, sporting black T-shirts and blue and black rucksacks that were slung casually over their shoulders.

But there was nothing casual about the way they mowed down passengers in the waiting hall. They turned the 19th century design gem with its heritage-protected architecture into a killing zone, stopping to reload their automatic weapons and shoot again.

Afterwards, the terminus, formerly known as Victoria Station, would be a bloodstained mess. Piles of abandoned luggage, spattered with red, were the eerie legacy of the many wounded, while the corpses of those who had not been so lucky littered the floor, their legs bent awkwardly underneath them from the force of the fall under a hail of bullets.

Then came a flurry of security alerts. An explosion at the Mazagaon Docks, one of India's largest ship-building sites; and shooting at a hospital where some victims were caught up for a second time. Another expat institution, Café Leopold had also been hit.

The popular bar-cum-restaurant on the Colaba causeway, the nerve centre of Mumbai, has always been popular for its cheap beer and greasy snacks and is known as the place for tourists to visit should they want to land a Bollywood role. In recent years, it has developed new-found fame because of its immortalisation in the best-selling novel Shantaram by the Australian author Gregory David Roberts.

David Gross, the boyfriend of an Australian soap star was among those soaking up the ambience on Wednesday night. Until, that is, the gunmen stormed in. Soon, the militants were engaged in a firefight with the police, bullets riddling the walls. Mr Gross hid with other customers as best he could in an upstairs room, before eventually climbing out of a window.

"There were grenades going off, we started breaking the windows and ripped down curtains to make a rope ... people were sliding out, like you're taught to do," he said. "It was a one-storey drop on to broken glass."

By then, India's emergency services had a struggle on their hands and explosions at the Taj Mahal and Trident-Oberoi hotels had made matters worse, starting fires in the lobbies.

By 11.52pm, the flames had begun to spread. People were being evacuated from the two buildings, with the injured and incapacitated wheeled out on golden luggage trolleys.

Steve Loschko, an American backpacker, was staying in a hostel across from the hotel. He watched, stunned and horrified, as the fire spread.

"On the top floor I could see a man, who was standing there shouting, 'help me, help me'. The fire brigade hosed him with water. I presume that he had been on fire." The silhouettes of some of the guests trapped inside could be seen at windows of the hotel. Fists were raised against the glass, lights were flicked on and off to attract attention, one couple took turns to wave a white flag while another guest banged a large lamp against the pane.

By midnight, reports began to emerge of another deadly twist to the terror – the gunmen had been specifically looking for British and American tourists.

"They told everybody to stop and put their hands up and asked if there were any British or Americans," said Alex Chamberlain, a British sports writer who had been dining in one of the hotel's restaurants before managing to escaping.

"My friend said to me, 'Don't be a hero. Don't say you are British'." The segregation by nationality was a bitter irony for a hotel built in 1903 by Tata founder Jamsetji Tata, after he was snubbed at another plush establishment because he was Indian.

With hostages now feared to be in the hands of the militants, the state's anti-terrorism police began to close in on the attackers. It was a deadly undertaking and, by 1.35am, Hemant Karkare, Mumbai's anti-terror chief, was reported dead, killed in a gunfight with the militants that had taken his specialist team unawares. Exchanges of fire and explosions continued to rock this shaken city throughout the night, as images were beamed around the world of Mumbai's landmark buildings under siege. At 2.35am, a group called the Deccan Mujahideen, claimed responsibility for the attacks, but that only added to the confusion, given no one had ever heard of a such a group before.

An hour later, thick clouds of black smoke could be seen rising from the top of the Taj Mahal hotel. Some guests decided to make a bid for freedom, removing their shoes so that the terrorists could not hear them escape. Firecrews battled to rescue guests who were trapped inside by the smoke rather than by the hostage-takers, plucking the shell-shocked men and women from the balconies.

Ms Bains was among those rescued. "At about 4.30 in the morning, I saw a sight that I will never forget – it was the face of a fireman," she said. "It was the happiest moment of my life. He smashed the window and we climbed down a ladder to freedom."

VS Naipaul once famously said "Mumbai is a crowd". But as dawn broke on Thursday, the city was eerily quiet, pulsing not with hoards of Mumbaikers going about their hectic daily business, but with one unanswered question. Why on earth had this happened?

Survivor's story: 'I was incredibly lucky'
^{British MEP Sajjad Karim}

"At one point we had a gunman with amachine gun standing right in front of us, and he just started to point the gun and to shoot right at us. People in front of me started to fall. And a few of us were lucky enough and managed to get away from the lobby to a restaurant area where we could barricade ourselves in, so we were relatively safe. We just had to wait for the army to get in and come and rescue us. Today the situation is very tense. Mumbai is a city that's normally full of life... today it's a different city, it's no longer Mumbai."

Survivor's story: 'I prayed someone would find us'
^{Businesswoman and shop owner Dalbir Bains}

Ms Bains moved from the UK to Mumbai three years ago to set up a lingerie shop.

"When the attack began we were sitting around the poolside at the back of the hotel discussing business. We heard rapid gunfire break out. At first we thought it might be fireworks. Staff ushered us into a room, locked the doors and turned off the lights. They then put furniture against the door. The gunmen were running up and down the corridor firing indiscriminately. It was terrifying. The gunfire was continuous. We heard a series of explosions. At one point a bullet came through the wall and hit a water pipe. A couple of hours later we could smell smoke. We just kept absolutely silent and prayed. At 4.30 in the morning I saw the face of a fireman. He smashed the window and we climbed to freedom. It was the happiest moment of my life.