Five men were charged on Thursday in connection with an attack by Somali Islamist gunmen on Garissa University in northeast Kenya that killed 148 students, the worst militant attack in the east African nation in almost two decades.

The assault on Garissa University on April 2, in which gunmen from Somalia's al Shabaab group stormed in and sought to kill Christian students, has piled pressure on President Uhuru Kenyatta to do more to secure the border and other regions.

The effects of the assault are still being felt in Garissa County, where almost two-thirds of schools have had to shut because students, many from other regions, are not willing to go to school there any more, regional officials said.

Four men from Kenya and one from Tanzania were charged in court for conspiring to commit "a terrorist act at Garissa University College" and other related offences, court documents showed.

They are the first people to face formal charges over the attack.

Chief Magistrate Daniel Ogembo told the Nairobi court that a hearing would be held on July 11 to rule on whether to grant bail to the men accused of involvement in the attack, the worst since al Qaeda bombed the U.S. embassy in Kenya in 1998.

Kenyatta has faced mounting criticism for not doing enough to halt a spate of attacks by al Shabaab, which has vowed to keep up assaults until Nairobi pulls its troops out of Somalia where they are part of an African Union peacekeeping force.

Diplomats and security experts say the security services do not coordinate properly due to rivalries and the police often use heavy-handed tactics of mass arrests that undermine efforts to build intelligence on militant cells.

As well as Garissa, there have been assaults in the border region, along the coast and in the capital, including the 2013 Westgate shopping mall attack in which 67 people were killed.

The region along the long Somali border, already a desperately poor area, has been particularly hard hit.

"There are about 96 schools which have closed in a span of a few weeks because of security fears," Harun Rashid Khator, Garissa County commissioner, told Reuters, saying that was out of a total of 150 primary and secondary schools in the county.

About 1,300 teachers work in the schools and many have refused to return to work, with primary schools the most affected. Khator said efforts to hire new teachers drew a poor response.

Garissa County Governor Nathif Jama said officials were appealing to the government to help. "This is going to affect the future economy and social life of this area badly if the national government doesn't treat it with urgency now," he said.