Four gunmen wearing suicide vests were locked in a gunbattle with Afghan security forces inside a building in southern Afghanistan on Friday, a police official said. Abdul Qayum, a senior police official at the scene, told Reuters he could hear the sound of rocket-propelled grenades and heavy gunfire. He did not have any more details. Earlier this month, Taliban gunmen launched a brazen assault inside the centre of the capital Kabul, with suicide bombers blowing themselves up at several locations and militants battling security forces from inside a shopping centre.