Updated

The Latest on a roadside bomb blast in Kenya (all times local):

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3:40 p.m.

A Kenya official says an improvised explosive device has killed four passengers traveling in a vehicle in the country's north in a suspected extremist attack.

The official, who spoke on condition of anonymity because he is not authorized to speak with the press, says the vehicle had 15 people on board and the other 11 are critically injured.

Mandera County commissioner Fredrick Shisia says the vehicle is used commercially along the Elwak-Mandera route.

Similar explosions in Kenya in the past month have killed at least 34 people, including 20 police officers. Suspicion has fallen on al-Shabab extremists from neighboring Somalia.

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2:35 p.m.

A Kenyan official says a vehicle with 24 passengers has been blown up by an improvised explosive device in the country's north in a suspected extremist attack.

Mandera County commissioner Fredrick Shisia said Friday they are waiting for word on casualties. Shisia says the vehicle is a privately owned transport service along the Elwak-Mandera route.

Similar explosions in Kenya in the past month have killed at least 34 people, including 20 police officers.

Suspicion has fallen on al-Shabab extremists from neighboring Somalia.

Analysts call the blasts a change in strategy by al-Shabab, which has been carrying out attacks inside Kenya since 2011. The extremist group has called the attacks revenge for Kenya sending troops to Somalia to fight it.