BAGHDAD (Reuters):

United States and Iraqi forces killed 50 people yesterday in raids on a Sunni Arab district they described as riddled with "terrorist hideouts" and a hotbed of insurgent activity by foreign fighters linked to al Qaeda.

As American helicopter gunships and ground attack jets kept up vigil over central Baghdad, Defence Ministry spokesman, Major General Ibrahim Shakir, said 50 had been killed and 21 people arrested in the operation around Haifa Street, where officials have said more than 130 people have died since Saturday.

U.S. and Iraqi forces clashed with gunmen, saying they came under fire from mortars and rocket-propelled grenades.

Battling growing sectarian violence, Shi'ite Prime Minister Nuri al-Maliki announced a major security plan for Baghdad on Saturday, vowing to crack down on violence on all sides, regardless of "sect or political affiliation".

It was not clear if the Haifa Street operation marked the start of the implementation of the plan, but it was the most sustained action by U.S. and Iraqi troops in recent days. U.S. President George W. Bush is set to unveil a new strategy in Iraq today, expected to involve more U.S. troops for Baghdad.