Kenyan churches used armed guards to protect their Easter congregations on Sunday, days after gunmen from the Islamist al Shabaab group killed nearly 150 people at a Kenyan university.

Kenyan priests, who have been frequently targeted by Islamists, said they feared churches could be targeted on Easter Sunday, the main liturgical feast in the Christian calendar.

"We are very concerned about the security of our churches and worshippers, especially this Easterperiod, and also because it is clear that these attackers are targeting Christians," Willybard Lagho, aMombasa-based Catholic priest and chairman of the Coast Interfaith Council of Clerics (CICC), told Reuters.

He said churches in the Indian Ocean port city of Mombasa were hiring armed police and private security guards for mass on Easter Sunday. Christians make up 83 percent of Kenya's 44 million population.

Four masked militants from the Somali Islamist group stormed a university campus in Garissa on Thursday, seeking out Christian students to kill while sparing some Muslims.

Al Shabaab group said the assault on Garissa, some 200km (120 miles) from the Somali border, was revenge for Kenya sending troops into Somalia to fight alongside African Union peacekeepers against the al Qaeda-aligned group.

The militants have threatened to turn Kenyan cities "red with blood" with more attacks. Police have stepped up security at shopping malls and public buildings in the capital Nairobi, and in the eastern coastal region which has been prone to al Shabaab attacks.

In Nairobi's Holy Family Basilica cathedral, nestled between the City Hall and Kenya's parliament, two uniformed police officers armed with AK-47 rifles manned the entrance gate. One officer said more plain clothes officers were inside.

Three private security guards frisked churchgoers with hand-held metal detectors, while a fourth guard used a mirror to check for explosives underneath cars.

"Everyone is anxious and you never know what will happen next, but we believe the biggest protector is God and we are praying," said Samuel Wanje, 27, a youth member at the church.

In Garissa, where masked gunmen in 2012 killed more than a dozen people in simultaneous gun and grenade raids on two churches, six soldiers guarded the town's main Christian church and about 100 worshippers ahead of Sunday mass.

"Nowhere is safe, but here at church you can be with God and console yourself," said Meli Muasya at Garissa's walled Catholic Church.

HEIGHTENED SECURITY

Kenya has imposed a dusk-to-dawn curfew in four counties along its 700km border with Somalia and deployed helicopters along its palm-fringed coast, popular with Western tourists and the scene of Islamist attacks in the past.

Coastal Region police chief Robert Kitur told Reuters extra uniformed and plain-clothes police officers had been deployed.

"What happened in Garissa must never be seen in Mombasa or anywhere else in the region and country," he said.

Late on Saturday, 613 students and 50 staff from Garissa University College arrived in Nairobi to an emotional welcome by parents and relatives. Parents of missing students attempted to identify bodies at the city's mortuary.

Garissa was the most deadly attack on Kenyan soil since al Qaeda in 1998 bombed the U.S. embassy in Nairobi, killing more than 200 people and wounding thousands of others.

The attack has further strained the historically cordial relations between Kenya's Christian and Muslim communities, which have deteriorated due to frequent Islamist attacks on Christian priests and churches.

President Uhuru Kenyatta is under pressure to halt Islamist attacks that have hit Kenya's important tourist industry hard. On Saturday he said Garissa's attackers were "deeply embedded" in Kenya's Muslim community, which must do more to fight radicalization.

Al Shabaab has killed more than 400 people on Kenyan soil since Kenyatta came to power, including 67 who died in a raid on Nairobi's upmarket Westgate shopping mall in 2013.

Most upscale hotels in Nairobi have installed thick metal gates and airport-style X-ray machines since then. Extra security checks are performed on vehicles entering restaurants, malls and other sites popular with Westerners.

"All the mall owners, who take security very seriously, revised their security measures before Easter. But after the Garissa attack, they increased it again," said Peter Bach, global managing director of security firm Diplomatic Protective Services.