The Kenya Red Cross on Sunday said that there had been "at least three separate grenade attacks" and that the grenades had been thrown from a speeding vehicle.

The blasts follow a recent grenade attack outside a mosque that killed at least five people as well as wounding the local member of parliament.

A recent roadside bomb in Eastleigh district killed one person and wounded several others. And last month, a bomb on a bus killed nine people.

Kenya has suffered a string of attacks, often blamed on al-Qaeda-linked al-Shabab fighters, since it invaded Somalia last year.

Kenyan troops, now integrated into an African Union force, seized the Shabab bastion of Kismayo in September, a key southern Somali port. That led to warnings of retaliation from both the insurgents and their Kenyan supporters.

But the Shabab have denied involvement in previous similar bombings.

Violence in Kenya - ranging from attacks blamed on Islamists, inter-communal clashes and a police crackdown on a coastal separatist movement - have raised concerns over security ahead of elections due in March 2013.

Last month, riots broke out in Eastleigh after the bombing of a bus, with running street battles between demonstrators and the police.