Three people were killed and at least 60 wounded when two homemade bombs exploded on buses travelling along one of the busiest roads in the Kenyan capital, Nairobi.
Of the 60 wounded, 20 were in a critical condition, according to the National Disaster Operations Centre.
The blasts were on two buses packed with commuters along Thika Highway, said Moses Ombati, the deputy police chief in Nairobi. Eliud Lagat, the deputy head of the bomb disposal unit, said the blasts were caused by improvised explosive devices.
The explosions come a day after two blasts at the Kenyan coast killed four people. Police said a grenade thrown at a bus stop in the coastal town of Mombasa killed the four. The second blast at a public beach did not cause any fatalities.
Kenyan president Uhuru Kenyatta, reacting to the blasts at the coast, said that terrorists want to provoke a sectarian war.
"The terrorists would like a war of religion, bringing to an end our history of tolerance. This country will not allow it. The terrorists will be treated as the vicious criminals they are, and our tradition of easy coexistence will be maintained," Mr Kenyatta said.
"The terrorists wish to see us despairing and divided," he said. "They will be disappointed."
Kenya has been hit by a wave of gun and explosives attacks since it sent troops to neighbouring Somalia to fight the Islamic extremist rebels, al-Shabab, in 2011. The al Qaida-linked militants have vowed to carry out terrorist attacks in Kenya to avenge the presence of Kenyan troops in Somalia.
Terror warnings have been a constant in Kenya in recent months, particularly after the attack on Westgate Mall killed at least 67 people in September. Al-Shabab claimed responsibility for that attack.
Last month, a car bomb exploded outside a police station in Nairobi, killing two officers and two men of Somali origin inside the vehicle. Police had impounded the car for driving on the wrong side of the road. Three ethnic Somalis have been arrested over the blast, and are expected to be charged in court this week.
Since last month, Kenya has been conducting a security operation in response to the terror attacks. Thousands of people, mainly ethnic Somalis, have been arrested in the security sweep which has been heavily criticised by human rights groups who say officials have carried out abuses.
Police say the operation is aimed at weeding out terrorists and illegal aliens from war-torn neighbouring countries, who are blamed for smuggling small arms and other weapons into Kenya through porous borders.
Rights organisations accuse the police of profiling Somalis, detaining suspects without trial, denying them representation, extortion, circumventing the courts to deport Somalis back home and holding the suspects in inhumane conditions.