Gunmen have killed 17 people and wounded dozens in gun and grenade attacks on two churches in the Kenyan town of Garissa near the border with Somalia.
Wearing balaclavas, the attackers killed two armed police - posted outside churches following previous attacks - before bursting inside to target worshippers as they held prayer services on Sunday.
Witnesses said bodies lay scattered on the floor inside the blood spattered buildings - a Roman Catholic church and an Africa Inland church.
"It is a terrible scene, you can see bodies lying in the churches," said regional police chief Leo Nyongesa.
At least 40 people were rushed to hospital, several in a critical condition, the Kenyan Red Cross said.
The Red Cross, which put the death toll at 17, flew the three most critically injured victims by air ambulance to the capital Nairobi.
Three children were reported to be among the dead.
"It is a horrible sight to see," said Hussein Abdi, a resident of Garissa, some 140 kilometres from the border with war-torn Somalia.
Kenya has suffered a spate of gun, grenade and bomb attacks since sending troops into southern Somalia last October to target al-Shabab rebels fighting to overthrow the weak UN-backed government in the Horn of Africa state.
Later, the pro-Shabab Twitter site Al-Kataib boasted of a "successful operation in Garissa" but did not specifically claim responsibility. Nairobi has blamed previous assaults on the al-Qaeda-linked al-Shabab.
Kenyan Vice President Kalonzo Musyoka said the nation "will not be intimidated by such cowardly acts" and urged Kenyans to "exercise religious tolerance".
The Supreme Council of Kenya Muslims condemned the attacks, saying that "all places of worship must be respected".
Police said up to seven men had carried out the attacks which came two days after a gunmen killed a Kenyan driver and abducted four foreign aid workers from the Dadaab refugee camp, some 80 kilometres to the northeast.
Last week a grenade blast in a bar in Kenya's main port of Mombasa killed three people, a day after the US embassy warned of the threat of attack.
Search efforts continued for the abducted aid workers, two men and two women who work with the Norwegian Refugee Council.
Kenya's army scoured border areas amid fears the gunmen and their hostages had crossed into Somalia, around 100 kilometres from Dadaab, the world's largest refugee camp.