It was the worst day of foreign abductions in the increasingly chaotic and hostage-prone Gaza Strip since Israel withdrew its troops and settlers from the territory last September.
Two French journalists and a South Korean journalist remain hostages in the custody of Palestinian fighters in Gaza.
A US teacher of English at the Arab American University in the northern West Bank town of Jenin, Douglas Johnson, 45, was also briefly kidnapped by Palestinian fighters.
An armed group set free a Swiss employee of the International Committee of the Red Cross, Julien Grosclaude, whom they abducted in Gaza.
Two Australians, taken from a school in northern Gaza, have also been released.
Palestinians in Gaza staged angry and violent protests on Tuesday after British and American monitors withdrew from the prison in Jericho and Israeli troops quickly moved in to capture prisoners.
Palestinian fighters and police exchanged fire at a British cultural centre in Gaza city, as troops tried to prevent hundreds of protesters from reaching the building.
The angry protests in Gaza began with fighters firing shots at a British cultural centre and briefly storming the offices of AMIDEAST, a private organisation that provides English classes and testing services.
The British Council in Gaza was
the target of mob violence
With the rampant insecurity increasingly threatening to escalate out of control, Palestinian police shot dead a fighter from the Popular Front for the Liberation of Palestine (PFLP) and wounded seven others in the Gaza Strip.
About 300 Palestinians led by armed men marched towards the British cultural centre. Palestinian police surrounded the office and tried to keep the crowd away. Both sides fired in the air and then exchanged fire, but there were no immediate reports of injuries.
US and British inspectors had left the Jericho prison, and Israeli forces arrived shortly after their departure to arrest a Palestinian leader there.
The foreign inspectors had been supervising the imprisonment of the leader and those involved in the assassination of an Israeli cabinet minister in 2001.
A spokesman for the al-Aqsa Martyrs Brigades, Abu Qusai, said US and UK citizens had two hours to leave the Palestinian territories.
"We call upon all American and British citizens to leave Palestinian territories immediately otherwise they will be subject to kidnapping and other consequences," he said.