GAZA CITY, Gaza Strip (AP) – Rampaging Palestinian policemen, furious over the killing of a colleague, took over the Gaza-Egypt border crossing for several hours Friday, forcing European monitors to flee, in the latest sign of growing mayhem in the coastal strip.

Gaza has experienced a wave of shootouts, kidnappings and armed takeovers of government buildings in recent months, undermining Palestinian leader Mahmoud Abbas’ efforts to impose law and order in the wake of Israel’s withdrawal from the area in September. In new violence, a 14-year-old boy was killed Friday when a powerful Palestinian family attacked a local police station for a second straight day.

With Friday’s border takeover, along with this week’s kidnapping of a British aid worker and her parents, the chaos appears to be spreading to outsiders brought in to help develop the area following Israel’s pullout.

Palestinian security forces reported progress in their search for the British hostages, who were kidnapped Wednesday, but conceded they still did not know who had seized the family or where they had been taken.

About 100 policemen stormed the Rafah border terminal Friday morning, firing in the air and taking up positions at the crossing, security officials and witnesses said.

The unarmed European observers — responsible for enforcing terms of the Israeli-Palestinian agreement that opened the border last month — then took refuge in a nearby Israeli military base, forcing the terminal to halt operations.

The police withdrew peacefully from the border after about three hours. Several hours later, the Europeans reopened the crossing, said Julio De La Guardia, a spokesman for the observers.

The unrest could threaten international efforts to help rehabilitate Gaza, whose economy is in tatters as it emerges from five years of heavy fighting with Israel. Under the leadership of former international envoy James Wolfensohn, donors have pledged $3 billion annually for Palestinian reconstruction projects, mostly in Gaza, for the next three years.

The Rafah terminal was opened last month under an agreement negotiated by Secretary of State Condoleezza Rice. The deal opened an important lifeline for Gaza’s economy and marked the biggest diplomatic breakthrough since the Israeli withdrawal.

Israel closed the border shortly before the pullout, fearing militants would smuggle weapons into Gaza. The presence of the EU monitors was meant to address those security concerns. The crossing cannot operate if the European contingent is not present, De La Guardia said.

The angry police officers demanded the execution of the gunman who killed the officer Thursday.

The officer and a civilian were killed in a shootout that erupted between two rival families outside a police station. The violence began when one of the families approached the station to free a relative detained on drug charges.

Members of the incarcerated man’s family stormed the police station again Friday, sparking another shootout. A 14-year-old boy passing through the area was mistakenly shot in the head and died instantly, police said.

In the kidnapping of the Britons, Palestinian Interior Ministry spokesman Tawfiq Abu Khoussa said authorities had received a tip and were searching for a white Mazda believed to have been used in the abduction.

But Gaza’s police chief, Ala Housni, conceded the kidnappers had not contacted authorities or made any demands.

“These are enemies to the Palestinian people,” Housni said at a news conference. “We will get them. If we have to use force we will.”

The aid worker has been identified as Kate Burton, 25. Her father, Hugh, a retired European Union official, and mother, Helen, were visiting her on vacation when they were kidnapped by armed gunmen in Rafah, officials said.

There have been a string of kidnappings of foreign aid workers and journalists in Gaza in recent months, with gunmen usually demanding jobs, the release of relatives from prison or other favors from the government. The hostages have been released unharmed.

Abbas’ critics have accused him of giving in to kidnappers’ demands, encouraging more abductions.

Abbas has been reluctant to confront the militant groups and armed gangs, fearing it could lead to civil war. But frustration in the Palestinian public over the chaos could force him to make a move as he heads toward Jan. 25 parliamentary elections.

The Hamas militant group, running on an anti-corruption and law-and-order campaign, poses a serious challenge to Abbas’ Fatah Party.

A rift within Fatah between its veteran leadership and “young guard” has further weakened the movement.

Marwan Barghouti, the imprisoned leader of the young guard, apologized Friday for the party’s failures but urged Palestinians to give it another chance in the vote.

“We do not hesitate to apologize to the Palestinian people for the mistakes that have been committed in recent years, … and I call upon the Palestinian people to renew their confidence in Fatah and to give Fatah a new opportunity,” Barghouti said in a statement from his prison cell.

Barghouti, who is serving a life sentence in Israel for involvement in five murders, is heading Fatah’s list of candidates for the election.

The statement, to be published Saturday in Palestinian newspapers, was obtained by The Associated Press.