Somalia’s Shebab rebels on Monday denied being behind grenade blasts that killed six people in the Kenyan capital at the weekend, which Nairobi blamed on the extremist insurgents.

Somalia's Shebab rebels on Monday denied being behind grenade blasts that killed six people in the Kenyan capital at the weekend, which Nairobi blamed on the extremist insurgents.

"We are not actually involved in such low-scale attacks. Al-Shebab has nothing to do with the hand grenade attacks that hit Nairobi," said Sheik Mohamed Ibrahim, a senior Shebab official.

Kenya's Internal Security Minister on Sunday said they suspected the Shebab was responsible for the attack in which four grenades were thrown at a busy bus terminus on Saturday from a car driving past.

Al-Shebab has threatened Kenya since it sent its troops into Somalia in mid-October to dislodge the insurgents controlling swathes of the south, which it accused of a series of kidnappings and attacks on its territory.

The attack was the deadliest in Nairobi since one in June 2010 during a public meeting against the adoption of a new constitution, in which the death toll was also six.

Police said Monday they had arrested four suspects.

Despite the denial the Shebab official renewed the Al-Qaeda-linked insurgents' threats to launch more attacks.

"There will be a day we will hit their cities if they continue with their aggression," Ibrahim said.