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.