The shooting by fighters angry over the handling of ruling party primary elections, forced the closure of all Palestinian election offices in the West Bank and Gaza Strip on Tuesday.
About 100 members of the Al-Aqsa Martyrs' Brigades, the armed section of Fatah, the party of President Mahmoud Abbas, fired in the air as they burst into the election headquarters in Gaza City, shortly before rival Hamas members were expected to register their candidate lists for the vote.
At the same time, armed men raided election offices in the West Bank city of Nablus, and in Rafah and Khan Yunus in the Gaza Strip.
There were heavy clashes with police in Khan Yunus, but no immediate reports of casualties.
The men, who smashed desks and computers in the offices, threatened to prevent the elections from taking place unless Fatah conducted a repeat of primaries it halted in some areas.
The primaries have been tainted by violence and fraud.
Abu Iyad, a spokesman for the armed men, said the storming was just a first step.
Mahmoud Abbas has called for
urgent measures to restore calm
"This is a peaceful step to protest the policy of [candidate] appointments within Fatah," Abu Iyad said.
The men, who spent years battling Israel said they sometimes felt marginalised within Fatah because of the dominance of an Old Guard leadership. They fear they will not be fairly represented on Fatah's ticket unless the primaries are repeated.
Fatah's younger generation is also concerned that if Old Guard leaders hand-pick the candidates, rather than allowing them to be elected in popular primaries, the ruling party will be less able to fend off a Hamas challenge at the polls.
But new primaries are unlikely in light of a Wednesday deadline to register candidates for the polls. Extending that deadline would risk delaying the elections, which Abbas has repeatedly vowed to hold on time.
The violence highlighted growing unrest in Gaza after Israel's withdrawal in September and ahead of elections seen as a test of Abbas's leadership.
"This is a peaceful step to protest the policy of [candidate] appointments within Fatah"
Spokesmen for armed fighters
The resistance and welfare group Hamas, sworn to Israel's destruction, is expected to mount a serious challenge to Fatah's traditional dominance in parliament.
It also marked growing divisions within the ruling party.
Abbas condemned the violence, and called for urgent measures to restore calm.
He has struggled to impose order in Gaza, seen as a testing ground for Palestinian statehood since Israeli troops withdrew after 38 years of occupation.
A Fatah review board led by Abbas is already at work trying to determine who will run on his party ticket.
Election work halted
The Palestinian central electoral commission said on Tuesday it was suspending its activities in protest at the violence.
Commission president Ammar al-Dwaik said: "We have told all our employees to close and leave their offices."
Israeli troops shot dead a teen-
ager during a raid on Nablus
Also on Tuesday, Israeli forces killed two Palestinian civilians in the West Bank and Gaza Strip, Palestinian witnesses and medics said.
They said occupation troops shot and killed a Palestinian bystander and wounded 12 people in fighting between soldiers and Palestinian fighters during an Israeli raid in the West Bank city of Nablus.
Israeli troops firing into the Gaza Strip also killed a Palestinian man near Gaza's boundary with Israel where resistance fighters and soldiers have exchanged fire in recent days, witnesses said.
In Nablus, witnesses said Israeli soldiers opened fire after armed men, mingling with youths throwing stones at soldiers, shot at troops during an arrest raid. The wounded included stonethrowers and a fighter, the witnesses said.
The Israeli army said troops had fired towards Palestinian fighters who shot at them, but did not believe their fire had hit anyone. The army denied targeting stonethrowers.
Military sources said two soldiers were also lightly hurt from an explosive device thrown by Palestinians during the raid. They said armed men had opened fire several times at the troops.
In the Gaza Strip violence, witnesses said a Palestinian farmer on his way to his field was killed by Israeli fire from across the boundary line with Israel. Palestinian witnesses said the man, from Abassan village, was killed by a tank shell.