Nairobi, Kenya — Police Commissioner Mathew Iteere now says Sunday's grenade attack at a church in Ngara was carried out by a known Al Shabaab terrorist.
Iteere says the attacker who goes by the alias 'Amar' was in Kismayu, Somalia, last year but returned to Kenya early this year.
Police are now circulating his photo and urging Kenyans to volunteer information that may lead to his arrest.
"We are therefore appealing to anyone with information regarding his whereabouts to present it to the police. It is important to note that he is dangerous and believed to be armed with a pistol and may be in possession of explosives," Iteere said.
"It is instructive to note that Al-Shabaab through one of their leaders Sheikh Ismael Ali while addressing some members of the group within Kismayu claimed responsibility for the attack and vowed to dispatch more suicide bombers to Kenya."
One man was killed on the spot in the attack at the God's House of Miracles International Church in Nairobi's Ngara neighbourhood and 15 other people injured.
Nairobi has been hit by a series of attacks since late 2011.
The deadliest blast on March 10, was at a bus terminal in which nine people were killed and 60 others injured.
Police have blamed the strikes on Somalia's Al-Qaeda-linked Al Shabaab Islamists or their sympathisers, claiming the attacks are a response to the Kenyan army's invasion of Somalia, launched in October last year.
The operation aimed to curb the Al Shabaab influence in Somalia, where they control much of the south and central region in a country that has lacked a stable government for two decades.
The Ngara incident also came a week after the American Embassy in Nairobi warned of an impending terrorist attack in the capital city.
The mission had warned of an attack on government buildings and hotels, and cautioned its nationals to be extra vigilant.
Kenya sent its troops into neighbouring Somalia following a spate of kidnappings in the northern frontier and the coastal strip, which it blamed on the Islamists.