Gaza City, Gazy Strip ? Palestinian policemen went on a rampage over the killing of a colleague and seized 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.

Friday’s border takeover fed worries that chaos in Gaza may be spreading to outsiders brought in to help develop the area following Israel’s pullout.

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. Their assault the previous day caused the death of the police officer that set off the furious eruption by police Friday.

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

A Palestinian man looks Friday through the closed gate of the Rafah border crossing between the Gaza Strip and Egypt. About 100 Palestinian policemen, angry over the killing of a fellow police officer, stormed the crossing, firing in the air and forcing European monitors to shut the border and flee, Palestinian and European officials said. The incident was the latest in a rash of takeovers and kidnappings in Gaza that have undermined the rule of Palestinian leader Mahmoud Abbas.

The unarmed European observers – responsible for enforcing terms of the Israeli-Palestinian agreement that opened the border last month – 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.