(Adds Hamas comment) GAZA, Jan 3 (Reuters) - Two security officials loyal to Palestinian President Mahmoud Abbas were killed in Gaza on Wednesday in a clash with Hamas gunmen, hospital officials said. Abbas's Preventive Security force said the two were killed when a police unit from the ruling Hamas movement ambushed two of its vehicles in the southern town of Khan Younis. Hamas accused the Preventive Security force of firing first on personnel from the Hamas police unit in the area. A third Preventive Security official was in critical condition, hospital officials said.
