Five Palestinians fighters have been killed by Israeli fire in the Gaza Strip, officials and medics have said.

A spokesman for the Popular Resistance Committees said three of the group's members had been killed in an Israeli air strike over the northern Gaza Strip on Tuesday.

Islamic Jihad identified the two men killed in the other incident as members of their group.

The Israeli military confirmed it had carried out an air raid about an hour after two makeshift rockets were fired from the Strip.

Israeli authorities said the projectiles landed in open areas and caused no injuries.

Muawiya Hassanein, the head of Gaza emergency services, said the three Palestinians were killed in the northern Gaza Strip and had been brought to a morgue in Gaza City.

Israeli troops had earlier shot dead two Palestinian gunmen who had snuck across the border in the southern part of the territory, according to a military spokeswoman.

"There was an exchange of fire in which they were killed," she said, adding that no Israelis were wounded.

Tension in the Palestinian territories is high after Israeli naval commandos stormed a flotilla carrying hundreds of pro-Palestinian activists to Gaza on Monday, killing up to 10 people.