(Updates casualty toll)
BAGHDAD, Dec 17 (Reuters) - Twin bomb blasts killed 18 people and wounded 53 in central Baghdad on Wednesday as British Prime Minister Gordon Brown made an unannounced visit to Iraq, police said.
The car bomb and a second explosion killed police and civilians in the Nahdha neighbourhood of central Baghdad, near a traffic police station and a hospital.
Violence has dropped sharply in Iraq, where the U.S.-led invasion in 2003 unleashed years of sectarian bloodshed and insurgent attacks. But car bombs, assassinations and other violence are still routine.
Iraqi security forces, which are increasingly taking responsibility for imposing order as U.S. forces prepare to withdraw by end-2011, are frequent targets. On Monday, nine police were killed in Baghdad in a suicide bombing.
Brown arrived in Baghdad on Wednesday morning on his fourth visit as the British leader. He met Prime Minister Nuri al-Maliki and discussed plans to withdraw the remaining 4,100 British troops from southern Iraq by the end of July 2009.
Wednesday's bombings were some distance away, on the other side of the Tigris river from the heavily-fortified Green Zone where Brown met Maliki. (Writing by Missy Ryan; editing by Michael Christie and Andrew Roche)