"I urge expatriate Iraqis to return, especially doctors and other professionals, after the improvement in security and the success achieved by our armed forces in enforcing the law," Maliki said in a statement.

He said those Iraqis living overseas must take the opportunity to help rebuild the country as the improved security situation has started to "tempt international companies to seek work contracts in Iraq."

Tens of thousands of Iraqi doctors, professors and other professionals left the country after the first Gulf War in 1991 and then after the 2003 US-led invasion.

Brutal sectarian violence that broke out in 2006 prompted yet more to seek refuge overseas.

Hundreds of doctors, teachers and professors have been killed in recent years in Iraq by armed groups.

According to the United Nations about four million Iraqis have been displaced, with half fleeing to neighboring countries such as Jordan and Syria.