An Israeli air strike targeting a Hamas members killed two Palestinians in the Gaza Strip, dealing a blow to mounting expectation of an imminent truce announcement by armed Palestinian factions. A helicopter gunship fired two missiles at a vehicle east of the southern city of Khan Yunis, killing a 17-year-old girl and a 33-year-old man, Palestinian medical and security sources said. The army confirmed the raid, which wounded another 15 people, saying it was aimed at a car carrying a group of Ezzedin al-Qassam Brigade members on their way to fire mortars and homemade rockets at Israeli territory. The move provoked threats of revenge from Hamas' armed wing. "Faced by this aggression ... we cannot stay with our arms folded. We will hence answer, God willing, the crimes of the occupation," a statement said. And both Hamas and Islamic Jihad warned the attack could jeopardize the announcement of a ceasefire, with Hamas accusing Israel of deliberately trying to sabotage truce efforts. "This cowardly assassination confirms that the enemy does not want stability or quiet and hence puts real obstacles (in front of) our continuing inter-Palestinian dialogue and efforts towards a truce," senior official Ismail Haniya told AFP. The strike came hours after two other members from the Ezzedin al-Qassam Brigades were killed in a firefight with Israeli troops in the northern Gaza Strip area of Beit Hanun. Speaking on CNN shortly after the airstrike, Hamas official Ismail Abu Shanab dismissed media reports that a ceasefire deal had already been inked. "The three movements are discussing this issue seriously and, until this moment, nothing official has been declared," he said, saying talk of a ceasefire was premature. "I think we need some more time to reach an agreement, so let's wait until the official statement is declared." The Palestinian daily Al-Ayyam had quoted Palestinian sources as saying the factions had agreed that the situation was ripe for a truce and that it could be announced in Cairo by the end of the week. With the agreement apparently all but finalized, the truce proposal still had to be examined by Arafat. Palestinian officials explained that the agreement had already been delayed by the killing last week of Hamas military leader Abdullah Qawasmeh. Hopes of an imminent breakthrough in the conflict were also dampened when a new round of talks between Israeli and Palestinian security officials was postponed. The two sides have been discussing a partial army withdrawal from designated reoccupied areas, where the Palestinian security services would take over policing duties and prevent anti-Israeli attacks. Israeli troops continued their sweep for wanted militants in the West Bank on Wednesday, rounding up all the men in a village east of Jenin and arresting some 20 suspected activists in the town of Tulkarem, Palestinian security sources said. **PHOTO CAPTION*** Palestinian boys inspect a destroyed car near the southern Gaza Strip town of Khan Yunis, after Israeli helicopters fired several missiles at two cars, killing a man and a woman and wounding 15 other people. (AFP/Said Khatib)