A suicide bombing in Yemen's southern city of Ibb has killed at least 33 people, medical sources say.The blast appeared to be targeted at a cultural centre where members of the Houthi rebel group were gathered for a religious celebration.The governor of Ibb was thought to be among the injured, reports said.The Houthis, a Shia Muslim group, overran Yemen's capital Sanaa earlier this year, and have extended their influence in the following months.They have clashed with several tribal and Sunni militia groups, and have been fighting Sunni militants from al-Qaeda in the Arabian Peninsula (AQAP) since they overran the AQAP stronghold Radaa in October.No group has said it carried out Wednesday's attack. However, the Houthis have blamed AQAP for previous attacks.Mohammed Abdel-Baki, a spokesman for the Houthis, described the suicide bombing as a "massacre".These asswhipes were chanting death to America when the bomb went of.