Members of Somalia's al-Shabab armed group have hijacked a bus in Kenya and killed 28 non-Muslims on board after singling them out from the rest of the passengers.
Two police officers said that the bus travelling to the capital Nairobi with 60 passengers was hijacked 50km from the town of Mandera near Kenya's border with Somalia.
The officers insisted on anonymity out of fear of reprisals and because of an order from Kenya's police chief that officers should not speak to the media.
Al-Shabab claimed responsibility for the dawn attack in a statement on Saturday, saying it was revenge for raids carried out by Kenyan security forces on mosques in the coastal city of Mombasa. Kenyan police said they found explosives and arrested more than 150 people in the mosque raids.
"What happened in Mandera today we did in revenge for what the non-believer government has done to innocent Muslims," Sheikh Ali Mohamud Rage, a spokesman for the group, told Al Jazeera.
"They were attacked in places of worship and in their homes. They invaded the Muslim land fo Somalia ... It’s our duty to take revenge."
The interior ministry confirmed the attack, saying via its official Twitter handle: "Security agencies are in pursuit of the criminal gang. We'll give a comprehensive update once preliminary reports are out."
A reporter for Kenya's Standard newspaper told Al Jazeera the attack happened at 5:45am local time.
Quoting Mandera County Commissioner, journalist Boniface Mungeri said the attack was carried out by "about 100 gunmen who commandeered" the bus and forced the passengers out.
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Mungeri said the passengers were separated into groups according to their religion. Non-Muslims, the reporter said, were executed and Muslims were freed. The assailants attempted to take the bus but it got stuck in mud on the unpaved road.
"We killed the non-believers," Rage told Al Jazeera, confirming that they had split people up. "We did not touch the Muslims because they’re the ones we’re fighting for. The Muslims in Mandera and the Muslims in Somalia are the same to us."
Among those killed were two security officers and teachers who were travelling to their home towns on holiday.
Mandera County Governor Ali Ibrahim Roba said on Twitter: "The inhumane butchering of innocent Kenyans by terrorist must get [a] very firm response from our national security team."
Kenyan authorities have blamed al-Shabab for a wave of deadly attacks across the nation. Kenya sent troops to Somalia in 2011 after raids on its coastal towns blamed on al-Shabab and has since seen a surge in lethal attacks.
The Somali group has also been blamed for the September 2013 attack on the Westgate shopping mall in Nairobi, which killed 77 people.
Somali government troops backed by AU forces are making progress in capturing the remaining al-Shabab strongholds, but the group has continued to carry out attacks in Somalia and the East Africa region.
Al-Shabab was dealt a heavy blow following the death of their leader, Ahmed Abdi Godane, who was killed in early September in a US airstrike. Godane has since been replaced by Ahmed Omar, also known as Abu Ubeid.
Additional reporting by Hamza Mohamed. Follow him on Twitter: @Hamza_Africa
Source: Al Jazeera and agencies