GAZA/CAIRO, Dec 12 (Reuters) - Three members of the Islamist group Hamas were killed and others injured in a shooting on Sunday in the Palestinian camp of Burj al-Shemali in Lebanon, the group said, blaming the bloodshed on rival forces loyal to the Palestinian Authority. Two Hamas officials told Reuters earlier four people had been killed. The statement issued by Hamas said members of the National Security Forces, who belong to the Palestinian Authority, carried out the attack. Palestinian Authority officials condemned the attack, rejected Hamas" allegation and urged all sides to wait for the results of an investigation. The Palestinian Authority and Hamas have been bitter rivals since the 2007 brief civil war in the Gaza Strip, which ended up in Hamas"s control, while the Palestinian Authority continued to have limited control of the Israeli-occupied West Bank. Several reconciliation attempts have since failed to end the power-sharing disputes between the two sides. The shootings took place during the funeral of a Hamas supporter who was killed in an explosion on Friday night in the camp in the southern Lebanese port city of Tyre. Members of Palestinian group Hamas carry their weapons during the funeral of a man who was killed in an explosion that occurred on Friday night in the Palestinian camp of Burj al-Shemali, in southern Lebanese port city of Tyre, Lebanon December 12, 2021. REUTERS/Ali Hankir Men carry the coffin of a man who was killed in an explosion that occurred on Friday night in the Palestinian camp of Burj al-Shemali, during his funeral in southern Lebanese port city of Tyre, Lebanon December 12, 2021. REUTERS/Ali Hankir A Palestinian gunman carries a weapon during the funeral of a man who was killed in an explosion that occurred on Friday night in the Palestinian camp of Burj al-Shemali, in southern Lebanese port city of Tyre, Lebanon December 12, 2021. REUTERS/Ali Hankir 1/3 Men carry the coffin of a man who was killed in an explosion that occurred on Friday night in the Palestinian camp of Burj al-Shemali, during his funeral in southern Lebanese port city of Tyre, Lebanon December 12, 2021. REUTERS/Ali Hankir "We hold the Authority"s leadership in Ramallah and their security services in Lebanon fully responsible for the crime," the Hamas statement said. The Lebanese army said one suspect in the shooting has been taken into custody by the Palestinian National Security. Speaking to Reuters in Ramallah by phone from Beirut, the Palestinian ambassador to Lebanon, Ashraf Dabour, rejected Hamas allegations. "This is a rejected and a condemned action... Investigation committees will reveal who stood behind it," Dabour said. "We have made contacts with Hamas leaders and demanded they wait for the investigation results." Hamas said in a statement on Saturday that the blast on Friday night was caused by an electrical fault in a warehouse containing oxygen and gas cylinders for COVID-19 patients, as well as detergents and disinfectants. read more A number of armed Palestinian factions, including Hamas and the Fatah movement, hold effective control over roughly a dozen Palestinian camps in the country, which Lebanese authorities by custom do not enter.