Police shot dead a couple suspected to be terrorists after they threw four grenades, wounding five officers in an overnight stand-off, a police official said Sunday.

Following a tip, investigators raided the apartment where the couple was staying in the Githurai Kimbo area on the outskirts of Nairobi Saturday evening and ordered them out of their house, said Boniface Mwaniki, the head of the Anti-Terrorism Police Unit.

The couple refused to surrender, threw grenades and used their eight-month-old baby as a human shield, said Mwaniki.

Police fired tear-gas repeatedly into the house, said a resident of the building. The baby was removed from the house unconscious and two grenades were found in the house, said Augustine Nthumbi, the officer in charge of the Githurai Kimbo.

The incident highlights the threat of Islamic extremist violence in Kenya.

The man killed was Kenyan national Felix Otuko, who was suspected of carrying out two grenade attacks in October 2011 — the first of a string of grenade and gun attacks in Kenya, said Mwaniki of the police anti-terrorism unit.

Mwaniki said Otuko was a member al-Shabab cell with another Kenyan national Elgiva Bwire Oliacha, also known as Mohammed Seif, who is serving a life sentence in jail for grenade attacks in Nairobi on Oct. 24, 2011 which killed one person and injured 20 others.

Investigations showed that Oliacha supplied Otuko with the grenades for the two attacks, Mwaniki said.

These attacks followed threats against Kenya from Islamic extremist rebels in neighboring Somalia. The al-Shabab radicals, who are allied to al-Qaida, vowed to attack Kenyan targets in retaliation for the Kenyan government's decision in Oct. 2011 to send troops into Somalia to battle against al-Shabab.

The Kenyan government sent troops into Somalia after several cross-border attacks and kidnapping of foreign tourists that were blamed on al-Shabab.

Al-Shabab was working to establish a new generation of East African jihadists, warned a report by the United Nations in July 2011. The extremists represent a new security challenge for the region and wider international community, the report said. The rebels recruited other Africans in addition to ethnic Somalis, said the report.

Kenyan police warn that some are being trained by al-Shabab in Somalia and then returning to Nairobi slums, a border region near Somalia and Kenya's Indian Ocean coast, warn Kenyan police.