A series of explosions in the Iraqi capital, Baghdad, has killed at least nine people and wounded about 20, officials say.

It is believed the three blasts were all aimed at the security forces.

The first blast was caused by a roadside bomb targeting an army patrol in a western area, quickly followed by a second bomb nearby, officials said.

A third blast reportedly struck as fire crews arrived on the scene of the first explosion.

Violence in Iraq has fallen sharply in recent years, although militants still carry out regular attacks.

The last US troops are due to withdraw from Iraq by the end of 2011.

However, the US and the Iraqi government are in talks over whether to retain a limited American presence into 2012.