Egypt has declared a state of emergency in the north and centre of the Sinai Peninsula after a suicide car bombing killed at least 31 soldiers.

The measures will begin on Saturday at 03:00 GMT "for [a] duration of three months," President Abdel Fattah el-Sisi said in a statement, in the wake of the deadliest attack on the security forces since the army deposed President Mohamed Morsi last year.

A three-day mourning period has been declared across the country, while a curfew has been put in place between 7pm and 7am in areas covered by the state of emergency declaration, according to state media.

Speaking after a meeting of the national defence council on Saturday, Sisi described the Sinai Peninsula as "a nesting ground for terrorism and terrorists".

"Egypt has been fighting terrorists for months," he said. "No one can drive a wedge between the Egyptians and their army."

The attack on Friday afternoon hit an army checkpoint at Karm al-Qawadeis, southwest of Sheikh Zuweid in Sinai, killing 28 soldiers.

Egyptian sources said the suicide car bomber detonated his explosives near the checkpoint's magazine, causing it and an army vehicle to explode. Fighters then attacked the site with guns and a rocket-propelled grenade.

The source said the group attacked as soldiers were on break inside their tents. State media reported that 30 other people were wounded, several of whom were in critical condition.

Three more members of Egypt's security forces were killed in a separate attack at a checkpoint outside nearby al-Arish. It was not immediately clear whether the dead were soldiers or police.

Soldiers killed

In an interview with Al Jazeera, Peter Bechtold, a former US State Department official, said that anger is brewing in the region following the removal and imprisonment of Morsi.

Bechtold quoted sources as saying that Ansar Beit al-Maqdis, the most active armed group in Egypt, may be linked to the attack.

The attack was one of the deadliest on security forces since Sisi, in July last year, toppled Morsi from the presidency, launched a crackdown on his supporters and declared his Muslim Brotherhood movement a terrorist organisation.

Hundreds of soldiers and police officers have been killed in attacks since last year.

Source: Al Jazeera and agencies