A Palestinian suspected of ordering a mortar attack on a Jewish settlement fired on Palestinian policemen who came to arrest him, the first show of resistance to Palestinian security forces enforcing a fledgling truce.

Three people were injured in the shooting at Gaza's Beach Refugee Camp just before midnight on Friday, a Palestinian police source said. It wasn't clear if the suspect was among the wounded.

Altogether, Palestinian police have arrested 12 people in connection with the mortar attack, which wounded four Israelis. Palestinian security chief Mohammed Dahlan has vowed that his forces will pursue militants who violate a cease-fire by militant groups that went into effect on Sunday.

Beyond policing the truce, Israel and the United States want the Palestinians to disarm and dismantle extremist groups, including Hamas and the Islamic Jihad, which have killed hundreds of Israelis in shooting and bombing attacks.

Palestinian Prime Minister Mahmoud Abbas has rejected a fight with the militants, fearing a civil war.

Several dozen Palestinian militants rallied late Thursday to protest the arrests, firing their rifles into the air.

Meanwhile, on Saturday, one Palestinian was killed and another was wounded in an explosion in southern Gaza, Palestinian security sources said.

The cause of the blast along Gaza's eastern edge with Israel was unclear. Palestinian police investigators said the two men might have accidentally set off an explosive device left behind by Israeli troops, who withdrew from Gaza this week.

An Israeli army spokesman said the blast may have been from an explosive device that blew up close to an Israeli army patrol in southern Gaza.

Although fighting has decreased dramatically under the cease-fire, which was followed by Israeli troop withdrawals from parts of Gaza and the West Bank town of Bethlehem, there have been scattered incidents.

An anti-tank missile was fired toward an army patrol at a Jewish settlement in Gaza and a grenade was lobbed at an army post along Gaza's border with Egypt overnight. No one was injured in those incidents, the army said.

Also Saturday, an Israeli armored vehicle was pinned down under gunfire in the West Bank town of Jenin for more than an hour, until backup forces rescued them, the military said. No one was injured in the shooting. The patrol entered the city after gunmen fired on Israeli forces guarding a nearby Jewish settlement.

Abbas is to meet with Israeli Prime Minister Ariel Sharon on Tuesday to discuss further troop pullbacks, which are part of a U.S.-backed peace plan that calls on Israel to withdraw to positions held before the outbreak of fighting in September 2000. As part of the plan, Palestinians must dismantle militant groups that have attacked Israelis.

A senior Israeli official said Friday that the rate and the scope of further Israeli withdrawals would depend on how quickly the Palestinians disarmed militant groups. "The faster they take control, the faster we move out," the official said, speaking on condition of anonymity.

In a meeting Friday, Islamic Jihad leaders urged Abbas to also make the release of Palestinian prisoners — especially women, children and those who've served long sentences — a high priority in his talks with Israeli officials, said Mohammed al-Hindi a leader of the group.

Also Saturday, Hezbollah guerillas in southern Lebanon fired 26 anti-aircraft missiles into Israel, damaging two homes and a parked car but causing no injuries, an army spokesman said.

Fragments from some of the missiles, launched in three separate salvos, landed in the northern Israeli town of Kiryat Shemona. The army would not say if any Israeli aircraft were flying in the area at the time.

A Lebanese army statement said an Israeli "reconnaissance plane" flew over the southern Lebanese cities of Sidon and Tyre before returning to Israeli airspace. The statement did not mention missile fire.

Hezbollah and Israel fought a bloody guerrilla war for 18 years in southern Lebanon before Israel's withdrawal in 2000. Since then, Hezbollah has fired missiles across the border especially in the area of Sheba Farms, an Israeli border outpost that Lebanon continues to claim.

Meanwhile, Palestinian Foreign Minister Nabil Shaath said Friday that Palestinians could be ready to hold general elections by October if Israel withdraws from major population centers, but that Yasser Arafat will likely stand as the only major candidate for president.

Arafat's re-election would likely frustrate Washington's moves to sideline him and nurture an alternative Palestinian leadership.