Egyptian authorities have ordered residents living along the country's eastern border with the Gaza Strip to evacuate their homes prior to their demolishing because the army plans to set up a buffer zone.

The measure comes four days after armed men attacked an army post, killing at least 31 soldiers in the restive area in the northeastern corner of the Sinai Peninsula.

After the attack, Egypt declared a state of emergency and a dawn-to-dusk curfew there. Authorities also indefinitely closed the Gaza crossing, the only non-Israeli passage for the crowded strip.

The buffer zone, which will include water-filled trenches to thwart tunnel diggers, will be 500m wide and extended along the 13km border, officials told the AP news agency. It aims to stop weapons and trafficking between Egypt and the Palestinian territory.

Army officers spoke to the affected residents in person and initially gave them a 48-hour ultimatum to leave, but put that on hold after they protested, officials said. Residents groups are now negotiating with local officials to see if they can extend the deadline.

The officials spoke on condition of anonymity because they were not authorised to talk to journalists.

Violence escalating

The Egyptian army has waged a broad offensive in northern Sinai against armed groups who have emboldened their presence in several areas in the neglected eastern region over the past three years, destroying much of the web-like network of smuggling tunnels that connected the area with Gaza.

Egyptian media has accused Gaza's Hamas rulers of meddling in Egypt's affairs, with some suggesting the group is supporting fighters inside Egypt since the military overthrew former president Mohamed Morsi last year.

Hamas officials denied any interference and criticised Egypt for imposing stricter border crossing rules.

Since Morsi's toppling, attacks against security forces in northern Sinai have escalated, something Egyptian authorities blame on Morsi and his allies.

Morsi's Muslim Brotherhood group, which has been branded a terrorist organisation, denied links to violence.

Another al-Qaeda-inspired group, Ansar Beit al-Maqdis, has claimed responsibility for a number of attacks. No one claimed responsibility for Friday's attack on the army post.

Source: Al Jazeera and agencies