Air strikes 'show anti-IS unity'
US president Barack Obama has said the participation of five Arab nations in air strikes against militants in Syria "makes it clear to the world this is not America's fight alone".
Mr Obama said the joint fight against the Islamic State (IS) will take time, but is vital to the security of the United States, the Middle East and the world.
The US-Arab air strikes on Monday night targeted the group's headquarters in eastern Syria.
Mr Obama said the US is "proud to stand shoulder-to-shoulder" with Bahrain, Qatar, Saudi Arabia, Jordan and the United Arab Emirates in conducting the strikes.
Mr Obama, speaking ahead of meetings at the UN General Assembly in New York, said: "We're going to do what's necessary to take the fight to this terrorist group."
US Army General Martin Dempsey, the top American military official, said the US and its Arab allies had achieved their aim of showing the extremists that their attacks will not go unanswered.
The US and five Arab nations attacked the Islamic State group's headquarters in eastern Syria in night-time raids on Monday using land-and-sea-based US aircraft as well as Tomahawk cruise missiles launched from two Navy ships in the Red Sea and the northern Persian Gulf.
American warplanes also carried out eight air strikes to disrupt what the military described as "imminent attack plotting against the United States and Western interests" by the Khorosan Group, a network of al-Qaida veterans working with the Yemeni branch of al-Qaida, known as Al-Qaida in the Arabian Peninsula, to encourage foreign fighters with Western passports and explosives to target US aviation.
Mr Obama said the US was "proud to stand shoulder-to-shoulder" with its Arab partners.
General Dempsey called the strikes an unprecedented coalition with Arab states and said the partnership had set the stage for a broader international campaign against the extremists.
He said: "We wanted to make sure that IS knew they have no safe haven, and we certainly achieved that."
Several hours after the Pentagon announced the air strikes against Islamic State targets, US central command said American warplanes also launched eight strikes "to disrupt the imminent attack plotting against the United States and Western interests" by the network of al-Qaida veterans - sometimes known as the Khorasan Group - who have established a haven in Syria. It provided no details on the plotting.
Gen Dempsey said the timing was influenced by a concern that word of strikes in eastern Syria could prompt the al-Qaida veterans to disperse.
Central Command said the bombing mission against that group was undertaken solely by US aircraft and took place west of the Syrian city of Aleppo.
It said targets included training camps, an explosives and munitions production facility, a communication building and command and control facilities.
The airstrikes against Islamic State targets were carried out in the city of Raqqa and other areas in eastern Syria. They were part of the expanded military campaign that Mr Obama authorised nearly two weeks ago in order to disrupt and destroy the Islamic State militants, who have slaughtered thousands of people, beheaded westerners - including two American journalists and one Briton - and captured large swathes of Syria and northern and western Iraq.
Central command said the US fired 47 Tomahawk cruise missiles from aboard the USS Arleigh Burke and USS Philippine Sea, operating from international waters in the Red Sea and the northern Persian Gulf.
US Air Force, Navy and Marine Corps fighter jets, drones and bombers also participated.
Syria's foreign ministry said the US informed Syria's envoy to the U.N. that "strikes will be launched against the terrorist Daesh group in Raqqa." The statement used an Arabic name to refer to the Islamic State group.
Rear Admiral John Kirby, the Pentagon press secretary, said the strikes were not coordinated with the government of Syrian president Bashar Assad, but added: "There was no resistance, no interaction with Syrian air forces or military defences" during the operation.
Russia's foreign ministry warned that what it called "unilateral" air strikes would destabilise the region.
"The fight against terrorists in the Middle East and northern Africa requires coordinated efforts of the entire global community under the auspices of the UN," the foreign ministry said in a statement.
Iran's president Hassan Rouhani said the strikes in Syria were illegal because they were not approved or coordinated with Syria's government.
In New York for the UN meetings, Mr Rouhani said that Iran condemns the Islamic State group and stands ready to help fight terrorism. But he said the US policy is confused because it simultaneously opposes the militants while also trying to undermine the government of Mr Assad.
In Syria, activists said the air strikes hit targets in and around the city of Raqqa and the province with the same name. Raqqa is the Islamic State group's self-declared capital in Syria.
Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, said: "There is confirmed information that there are casualties among Islamic State group members."
Rear Admiral Dempsey said Arab participation needs to extend beyond direct military roles to assisting in an international effort to undercut finances, recruiting and ideological support for IS.