Kenyan police have fired tear gas to end riots that broke out in the capital, Nairobi, after a grenade blast killed at least seven people. Shops were looted in the Eastleigh neighbourhood, as angry youths blamed ethnic Somalis for Sunday's explosion, a businessman said. Somalia's al-Qaeda-linked al-Shabab group has been blamed for a spate of attacks in Kenya in recent years. Meanwhile, two Kenyan soldiers have been shot dead near the Somali border. The two were part of the African Union mission in Somalia but crossed back into Kenya to repair their truck in the town of Garissa when they were attacked, an army spokesman said. Kenya sent troops across the border last year to fight al-Shabab but its forces have since been merged with the AU force in Somalia. 'Hundreds arrested' Al-Shabab has not commented on the grenade attack on a minibus in Eastleigh, known as "Little Mogadishu" because of its huge Somali population. The BBC's Duncan Munene in Nairobi says a strong contingent of police are trying to prevent clashes between rival groups who are facing off against each other in the area. "There is chaos. Several people have been injured but we are doing everything possible to contain the riots," Nairobi police chief Moses Nyakwama said, AFP news agency reports. Shops in the area are closed and most residents are staying indoors, our reporter says. Police used tear gas and fired into the air to contain the violence, AFP reports. Eastleigh Business Committee Secretary General Ahmed Gutale said groups of youth had looted Somali-owned shops on Sunday. Police have arrested hundreds of Somalis in a security operation following the explosion, he added. Our reporter said when he visited Eastleigh on Monday, he saw police loading about 20 youths into a truck. Residents told our reporter that police had broken down doors during house-to-house raids on Sunday, and had even arrested school children.