"On the Al-Shebab threats and attacks at the Machakos bus terminus, four highly suspected criminals were arrested and are undergoing intensive interrogation," Nairobi Provincial Police chief Antony Kibuchi said.
Six people were killed when four hand grenades were hurled at a crowd in the bus terminus in the Kenyan capital on Saturday, and more than 60 others were wounded.
The suspects, all of whom are believed to be Kenyan, and three of whom are reportedly minors, were being interrogated by specialised police units, including anti-terrorism officers, a police source said.
The Al-Qaeda allied Shebab has threatened Kenya since it sent its troops into south Somalia in mid-October to attack bases of the Islamic insurgents, whom it accused of a series of kidnappings and attacks on its territory.
One of the men arrested had been on a police wanted list in December accused of having links to Shebab and Kenyan affiliates.
Saturday`s attack was the deadliest in Nairobi since one in June 2010, not attributed to Islamists, during a public meeting against the adoption of a new constitution, in which the death toll was also six.
Neither attack came close to the devastating Al-Qaeda car bombing of the US embassy in August 1998 that killed 213 people and injured 5,000.
Last October, less than two weeks after the army sent troops and tanks into Somalia, two grenade attacks in the space of less than 24 hours killed one person and wounded 30. (*)
Editor: Kunto Wibisono
Copyright © ANTARA 2012
