"Amnesty International holds the Israeli authorities responsible for the safety of the detainees and staff in Jericho Prison," the group said in a statement posted on its website. The Israeli occupation army announced earlier the end of a day-long siege of Areha prison and the detention of Saadat and five others.
The PFLP leader has reportedly surrendered to Israeli troops at the besieged prison compound. Saadat has been jailed under US and British supervision since August 2002 after the PFLP claimed the 2001 killing of far-right Israeli tourism minister Rehavam Zeevi to avenge the assassination of Saadat's predecessor.
Amnesty renewed calls to the Israeli authorities "to end their policy of assassinations and excessive use of lethal force." UN Secretary General Kofi Annan called Tuesday for an immediate end to all violence in the Gaza Strip, following the Israeli raid.
Annan's spokesman, Stephane Dujarric, said the UN chief was "deeply concerned" by the death of several Palestinian police officers and the kidnapping of a number of international personnel.
Israeli troops had pounded the compound with tank and missile fire through the day in a bid to force Saadat's surrender. Two Palestinian security officers were killed and 23 other people were wounded in the Israeli operation.
Amnesty also accused the Britain and the United States of having "contributed to perpetuating an extra-legal arrangement over the past four years during which Ahmad Saadat and his co-detainees were held arbitrarily by the PA."
Arab League Secretary General Amr Moussa has accused the US and Britain of coordinating with Israeli occupation forces to detain the PFLP leader. The United States and Britain withdrew their monitors from the prison just minutes before the Israeli attack on security grounds.
"We hold responsible the American and British guardians who took responsibility to guard the prisoners," Palestinian President Mahmoud Abbas said in a statement.