Kenya says 2 police officers killed by improvised bomb

An improvised bomb exploded and killed two Kenyan police officers Thursday near the spot where four officers died the day before in a similar blast, officials said. Concerns are growing that the al-Shabab extremist group is turning its focus on Kenya after military pressure on its strongholds in neighboring Somalia.

Eleven police officers have been killed in a trio of attacks in northern Kenya over the past two days, and al-Shabab has claimed responsibility, according to the SITE Intelligence Group, which monitors extremist groups.

Kenya's national police chief Joseph Boinnet announced earlier this week that al-Shabab has been stepping up attacks inside the country after Somalia's government declared a new offensive against the extremist group.

In Thursday's attack, two injured officers were airlifted to the capital, Nairobi, after the blast struck their vehicle near the border town of Liboi, North Eastern Regional Coordinator Mohamud Saleh said.

Wednesday's two attacks killed eight police officers. In the first incident, a police vehicle heading toward Liboi was blown apart by an improvised explosive device. In the second, five members of Mandera County Gov. Ali Roba's security detail were killed in an ambush on his convoy.

Al-Shabab has carried out more than 100 attacks on Kenya since 2011, calling it retribution for Kenya sending troops to fight it in Somalia as part of an African Union mission. Mandera County has been hardest hit.

Kenya has managed to stop the frequency of al-Shabab attacks in its capital, Nairobi, and major towns, but human rights groups say the government uses methods such as extrajudicial killings that can fuel revenge attacks.