The Egyptian army defused Saturday a bomb on a railroad linking the canal cities of Ismailiya and Suez, as air strikes hit suspected militants in the Sinai Peninsula, officials said.

The country has seen an uptick in bombings and shootings, mostly aimed at the security forces, since hundreds were killed in clashes when police broke up two Islamist protest camps in Cairo on August 14.

Police called in the military experts to defuse the bomb after residents of a village near the railroad spotted it, the officials said.

Two mortar rounds and a rocket-propelled grenade were attached to a fuse and appeared to have been intended for a 6:00 am (0400 GMT) train.

Hours later, unidentified assailants hurled a grenade at a police station in Cairo, which exploded without causing any casualties, security officials said.

It was the third such attack in weeks on the police station in the working class neighbourhood of Boulaq al-Daqrour.

The discovery of the railroad bomb comes after a powerful explosion targeted Interior Minister Mohamed Ibrahim as he left his house for work on Thursday.

Ibrahim, who survived unscathed, said afterwards the country faced "a wave of terrorism" amid a police crackdown on Islamist supporters of deposed president Mohamed Morsi.

A senior health ministry official said one person wounded in the bombing died from his wounds on Friday.

Police say they suspect explosives were placed in the trunk of a car parked outside the minister's home, and detonated as his convoy passed.

The umbrella group of Islamists demanding Morsi's reinstatement denounced the assassination attempt, and said they remained committed to peaceful protests.

But analysts say rogue militants are likely to attempt to carry out attacks as the military and police continue rounding up Islamists.

The railroad between Suez and Ismailiya lies on the west bank of the Suez Canal, with the restive Sinai Peninsula to the east.

On September 1, the head of the Suez Canal Authority, Admiral Mohab Mamish, said a militant launched an attack against a Panamanian-flagged ship passing through the vital waterway.

He gave no details, but a video posted on YouTube showed two men firing rocket-propelled grenades against a cargo ship, causing no apparent damage.

It was not immediately possible to verify the authenticity of the video, which featured the black banner used by Al-Qaeda inspired militants.

Egypt closed its border crossing with Gaza on Saturday citing "security grounds," said Maher Abu Sabha, the crossing's director in the Islamist Hamas controlled Gaza Strip.

He said the crossing was closed until further notice.

The military is facing an insurgency in the north of the Sinai Peninsula, a haven for Qaeda-inspired militants who launch almost daily attacks against security forces.

And state media reported a number of people were killed on Saturday in the northern Sinai when military helicopters carried out air strikes on suspected militant hideouts.

The claim could not be immediately verified. The authorities have restricted access to the volatile north of the peninsula.

For years, Sinai has defied the central government's authority, with its Bedouin population complaining of poverty and discrimination.

But the surge in militant attacks there and elsewhere around the country have raised fears of a revival of the Islamist insurgency that plagued Egypt in the 1990s, badly damaging the tourism industry.

Many of Egypt's most lucrative tourist destinations are in southern Sinai, along its Red Sea coast.

Attacks have surged in the region since the revolution that ousted dictator Hosni Mubarak in February 2011, and they have intensified since the military toppled Morsi in a popuarly backed coup on July 3 this year.