The Israeli army seized three officials of the radical Popular Front for the Liberation of Palestine (PLFP) in Ramallah today.
The action came amid calls by Jewish settlers for the army to take stronger action against Palestinians.
Two of the PLFP officials - Mr Beshir al-Khiri and the group's spokesman, Mr Ali Jaradad, are senior leaders and the detentions come on the first anniversary of the assassination by Israel of Mr Abu Ali Mustafa, then leader of the movement.
There were further seizures across the West Bank, with three members of the militant Islamist group Hamas captured in the nearby village of Naama while ten other people were detained in Ramallah, Nablus, and Dura near Hebron.
The seizures come on the day the Israeli settlers' council began a campaign aimed at convincing the Israeli government to defeat "the Palestinians and finish the war".
The settlers' campaign comes two days after the Israeli chief of staff, Gen Moshe Yaalon, said "Palestinian terrorism was spreading like a cancer" and called for tough military action to "defeat the Palestinians".
In a statement, the settlers urged the government to order the army to continue its systematic sweeps across the Palestinians territories.
The settlers also backed Israeli Prime Minister Mr Ariel Sharon's other tough policies, such as his attempt to deter future attackers by rounding up their relatives, demolishing their houses and threatening them with expulsion to the Gaza Strip.
They condemned the joint security agreement under which the Israeli army is due to withdraw from areas reoccupied since the beginning of the intifadain exchange for a Palestinian crackdown on militants.
AFP