A soldier guards one of the stricken buses on Sunday

A day after four people were killed by a grenade thrown at a bus stop in Mombasa, three people have been killed and at least 60 injured in bomb attacks on two buses on Nairobi’s Thika Highway on Sunday.

The East African nation 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 for the blast, and are expected to be charged in court this week.

Kenyan President Uhuru Kenyatta has accused terrorists of trying 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,” Kenyatta said.

“The terrorists wish to see us despairing and divided,” he said. “They will be disappointed.”

Thousands of Somalis have been arrested in a security sweep 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. Human rights campaigners have accused the police of profiling Somalis, detaining suspects without trial, denying them representation, extortion, circumventing the courts to deport them back home and holding suspects in inhumane conditions.