(Updates with death toll at 3, background)
ISMAILIA, Egypt, Nov 3 (Reuters) - Three Egyptian policemen died on Saturday when gunmen fired on their car in the northern Sinai Peninsula city of al-Arish before escaping, security sources said.
Disorder has spread in Sinai since autocrat Hosni Mubarak was ousted in a popular uprising last year, with Islamist militants stepping up attacks on security forces and the Israeli border. Egypt's new elected Islamist president, Mohamed Mursi, has pledged to restore security in the poor, desert region.
A police source said Saturday's attackers were probably militants who Egyptian forces, in the biggest security crackdown Sinai has seen in decades, have been hunting since the ambush killing of 16 border guards on Aug. 5.
Two policemen died at the scene of the attack on the suburbs of al-Arish, the administrative centre of North Sinai, while one of the other two injured died at the hospital later after the attack, medical and security sources said.
The Aug. 5 attack - the deadliest in Sinai since Egypt's 1973 war with Israel - prompted the government to send in hundreds of troops backed by tanks, armoured vehicles and helicopters in a joint operation with police to raid militant hideouts, arrest suspects and seize weapons.
But efforts to impose central authority in the lawless desert region are complicated by the indigenous Bedouin population's ingrained hostility to the government in Cairo.
Armed men seized a military vehicle last month, ejected an officer and a soldier and then drove into the desert. (Reporting By Yousri Mohamed; Writing by Tamim Elyan; Editing by Mark Heinrich)