A blast in Eastleigh, the main Somali district of the Kenyan capital Nairobi, killed at least five people Monday, an official at the national disaster operations centre said.
"Police are securing the area for emergency response services," the official said. Eastleigh has in recent years been the scene of several explosions usually attributed by the police to Islamist extremists.
"We suspect it is a grenade," a police officer at the scene told AFP. People at the scene said the explosive appeared to have been hurled at a bus stop and an adjacent food stall as people made their way home for the evening.
The attack comes a week after six people died when assailants burst into a church in Likoni district close to the port city of Mombasa and opened fire on worshippers.
The latest attacks come amid heightened warnings of a threat of Islamist violence in Kenya and despite boosted security in major cities.
Kenya has been hit by a series of attacks since sending troops into southern Somalia in October 2011 to battle Al-Qaeda-linked Shebab insurgents.