Many Hamas leaders and activists in the Gaza Strip have gone underground for fear of being targeted by Israel, sources close to Hamas said Monday. Meanwhile, a Fatah legislator has called for the assassination of Israeli leaders. Ashraf Juma'a, a legislator from Rafah in the southern Gaza Strip, urged all Palestinian armed groups to form a joint cell whose members would be entrusted with killing Israeli leaders inside Israel and all over the world. Hamas urged its members to take precautionary measures following reports that Israel was planning to assassinate senior political and military officials of the Islamic movement. The measures include a ban on the use of cellphones and cars, as well as gathering in public places. Hamas spokesman Ayman Taha said the measures were taken because of the Israeli government's decision to resume targeted killings of Hamas and Islamic Jihad members. "We appeal to all our members to refrain from talking on their mobile phones and gathering in public places and to stop using cars for transportation, because there are many Israeli planes flying over the Gaza Strip," he said. "We must be on high alert and very careful." Thousands of Palestinians attended the funerals of seven people who were killed in an IAF air strike in Gaza City Sunday night. The victims were family members of Khalil Hayeh, a Hamas legislator and political leader. Addressing the crowd, Hayeh said Hamas was determined to pursue the fight against Israel. "Hamas will stick to the resistance against the occupation until we achieve victory," he said. "Even if you kill all our leaders, we will produce 1,000 great leaders," he added. "Today I'm proud that my family has joined the convoy of martyrs, and I pray to Allah that I may follow them." Palestinian Authority Prime Minister Ismail Haniyeh of Hamas attended the funeral, which turned into a large show of force in solidarity with Hamas. He urged the Palestinians to remain committed to the strategy of "resistance" against Israel, saying Israel's threats would not deter the Palestinians from achieving their goals. "We will continue with the resistance until we are either martyred or triumphant," Haniyeh said. "We don't care about our jobs and seats. They are not worth the shoe or drop of blood belonging to a Palestinian child." Izzadin Kassam (Hamas's military wing) said the Israeli threats were a "sign of Israel's bankruptcy" after failing to stop the Kassam rockets that are being fired from the Gaza Strip. "Israel's failure to halt the rocket attacks prompted it to perpetrate a massacre against Palestinian civilians," the group said in a statement, referring to Sunday night's IAF attack. "Israel is mistaken if it thinks that by targeting our leaders it will stop the resistance." In a related development, Fatah on Monday called for halting the Kassam attacks to avoid further bloodshed. "The rocket attacks are providing Israel with an excuse to kill our people and destroy our institutions," Fatah's central committee said a statement issued in Ramallah.