Kenyan police have named homegrown militant Islamist Mohamed Mohamud, a soft-spoken former teacher, as the alleged mastermind of the massacre of 148 people in a university in Garissa.

Known also by the alias “Kuno”, as well as “Dulyadin” and “Gamadhere” -- meaning "long armed" and "ambidextrous" -- the alleged Shebab member is also wanted in connection with a string of recent cross-border killings and massacres in Kenya's northeastern border region.

Kenya said Saturday it had arrested five men in connection with the university massacre by Somalia's Al-Qaeda-linked Shebab militants that left nearly 150 people dead.

The arrests came as militants warned of "another bloodbath" and a "long, gruesome war" unless Kenya withdrew its troops from Somalia.

The Pope led Catholics in prayer for persecuted Christians around the world at a Good Friday service in Rome, a day after 148 students and security officers were massacred by Shebab Islamists in Kenya.

A small group of believers carried a cross between 14 "stations" evoking the last hours of Jesus's life during the traditional Via Crucis (Way of the Cross) procession, as the Pope looked on.

The European Union pledged Friday to support Kenya's fight against extremism after 147 people were killed by Somalia's al-Qaida-affiliated Shebab Islamists in an attack on a university.

"Violent extremism has once again targeted the right of the people of Kenya to live in peace and freedom of religion," the bloc's foreign policy chief Federica Mogherini said in a statement.

Piles of bodies and pools of blood running down the corridors: survivors of the Kenya university massacre described how laughing gunmen taunted their victims amid scenes of total carnage.

Salias Omosa, an 20-year-old education student, said the victims were woken up at gunpoint in Thursday's pre-dawn attack, and Muslims and non-Muslims picked out by "how they were dressed".

The bodies of dozens of students massacred by Somalia's Shebab Islamists at a Kenyan university arrived in the capital Friday, as grieving relatives faced a desperate wait to receive the remains of their loved ones.

The day-long siege of Garissa University in which 147 people, mostly students, were killed was Kenya's deadliest attack since the 1998 bombing of the US embassy in Nairobi, and the bloodiest ever by the Al-Qaida-affiliated militants.

President Barack Obama's Kenyan grandmother, known as Mama Sarah, has welcomed his planned visit to the East African nation saying it will fulfill a promise he made to her years ago.

"He told me that he was waiting for political stability in the country before he can come," said Sarah Onyango Obama, who is in her early 90s, speaking of the July visit announced earlier this week.

Masked gunmen from Somalia's Shebab Islamist group stormed a Kenyan university Thursday as students were sleeping, hurling grenades and shooting dead at least 15 people before taking Christians hostage.

Scores of others were wounded in the assault, still ongoing over 12 hours after the first grenades were used to blast open the gates of the university in the northeastern town of Garissa, near the lawless border with war-torn Somalia.

A key trial in Uganda of 13 men accused of taking part in Al-Shebab bombings that killed 76 people in 2010 was postponed Tuesday after the top prosecutor was shot dead.

Police on Tuesday vowed to catch the killers of Joan Kagezi, acting assistant director of public prosecution, who was murdered by men on a motorbike as she drove home with three of her children on Monday evening.

Barack Obama will make a long-awaited trip to Kenya later this year, visiting his father's homeland for the first time since becoming U.S. president six years ago, the White House said Monday.

During the long-promised visit this July, Obama will attend a Global Entrepreneurship Summit in the east African nation, a statement said.