Three Palestinians have been killed by an Israeli tank shell in central Gaza according to Palestinian security sources. The incident took place near the al-Burij refugee camp late on Thursday, they said. There were no further details and their identities were not immediately known. The deaths bring the number of people killed since the beginning of the Palestinian intifada in September 2000 to 4,554, including 3,520 Palestinians and 960 Israelis. **Airspace violation*** In other developments, Israeli aviation violated Lebanese airspace over the south of the country several times on Thursday, the United Nations office in Beirut reported. "As of 3:45 pm (1345 GMT), eight violations, involving 11 aircraft and three drones, were recorded," said a UN statement, adding that "there have been no reports of any ensuing anti-aircraft fire across the Blue Line." The statement said Staffan de Mistura, the personal representative in Lebanon of UN Secretary General Kofi Annan was "concerned" by the violations of the Blue Line drawn between the two countries after Israeli forces withdrew from southern Lebanon in 2000. The over-flights occurred amid confusion over the deteriorating health in a French hospital of Palestinian leader Yasir Arafat. At around the same time, Israeli forces in the West Bank and Gaza were placed on a state of alert, security sources said. **PHOTO CAPTION*** In this handout picture from the Palestinian Authority's archives, dated mid 1990s, Yasser Arafat is seen posing with his daughter Zahwa in Gaza City. (AFP)