Six security forces and 21 rebels were killed in new clashes with followers of a Shiite rebel leader in Yemen, a security official said. Clashes broke out anew between the troops and the followers of Abdel-Malek al-Hawthi in Saada, about 180 kilometres north of the Yemeni capital.The fighting first erupted last week, with more than 100 people killed since. The official, who spoke on condition of anonymity because he was not authorised to talk to the media, said that 21 other members of the troops were also wounded in the latest fighting. Meanwhile, tribal and local leaders in Saada said that four civilians were killed after a rocket fell on their house last night. The reports could not be independently confirmed.