Hamas on Sunday dismissed as "unacceptable" Palestinian Authority Chairman Mahmoud Abbas's threat to arrest any Palestinian who violates the latest cease-fire with Israel. Meanwhile, several Palestinian armed groups warned that they would resume their attacks unless Israel also halted its military operations in the West Bank. At least three groups, including Islamic Jihad, have refused to sign on to the cease-fire agreement. One of them is the Aksa Martyrs Brigades, which said it would not abide by the cease-fire as long as Israel continued to arrest its members in the West Bank. The group, which belongs to Abbas's Fatah party, was responding to the arrest of Mahmoud Kadoura, a top member of the Aksa Martyrs Brigades, in Ramallah. Abu Obaidah, a spokesman for Hamas's armed wing, Izaddin Kassam, also warned that the cease-fire would collapse unless Israel stopped its military operations in the West Bank immediately. "The Israeli aggression must stop in both the West Bank and Gaza Strip," he said. "This is a temporary cease-fire and any Israeli assault on our people in the West Bank will be viewed as a violation of the agreement." Shortly after the cease-fire went into effect at 6 a.m. Sunday, Abbas ordered the deployment of some 13,000 PA policemen in the northern part of the Gaza Strip to stop the firing of rockets at Israel. Abbas also ordered the policemen to arrest anyone who violates the cease-fire. But sources close to Abbas expressed fear that Hamas would try to torpedo the deployment of the security forces. They also worried that some officers would refuse to carry out Abbas's instructions, either for political reasons or to protest unpaid salaries. Abbas's threat drew sharp criticism from Hamas, which warned against any attempt to arrest its members. "The era of political detentions has gone forever," said Khaled Abu Hilal, spokesman for the Hamas-controlled Interior Ministry, which is formally in charge of the PA security forces. Condemning Abbas's threat as "provocative," Abu Hilal said: "Such threats don't help preserve the cease-fire; on the contrary, they jeopardize the cease-fire. We urge those who are issuing threats to backtrack or to deny them." The Hamas spokesman nonetheless stressed his movement's desire to maintain the cease-fire on condition that Israel also abided by it. Ahmed Bahar, a senior Hamas leader in the Gaza Strip, claimed that the initiative for the cease-fire came from Israel, not the Palestinians. "The Israelis started begging for a cease-fire because of their defeat [in the Gaza Strip]," he told reporters. "The Palestinian resistance played an important role in repelling the Israeli army. The Palestinians are always triumphant." Ghazi Hamad, spokesman for the Hamas-led government, said representatives of all the armed groups were expected to hold a meeting late Sunday to assess the situation in the aftermath of the cease-fire announcement. "We want this agreement to succeed and take hold," he told The Jerusalem Post. "We will also launch an investigation into this morning's violations of the cease-fire. There is a consensus on the Palestinian side that the cease-fire must be based on the principle of reciprocity. I believe that all the groups are interested in maintaining this cease-fire." Earlier in the day, Hamas Prime Minister Ismail Haniyeh met with leaders of the armed groups and urged them to abide by the cease-fire. Following a similar meeting on Saturday night, Haniyeh phoned Abbas to inform him that all the groups had agreed to honor a conditional cease-fire with Israel. Abbas later phoned Prime Minister Ehud Olmert and told him about the decision. Explaining his organization's rejection of the cease-fire, Syria-based Islamic Jihad Secretary-General Ramadan Shalah said he was opposed to "partial truces" with Israel. "We have expressed reservations about this cease-fire because it applies only to the Gaza Strip and not the West Bank," he said. "It's not in the interest of the Palestinians to talk about a cease-fire in the Gaza Strip while Israel is continuing with its incursions, detentions and assassinations in the West Bank."