US and Iraqi military officials say attacks like this may rise ahead of US troop withdrawal by the year-end [Reuters]

A suicide bomber blew up an explosives-filled vehicle at the entrance to a special police unit in Iraq's southern oil port of Basra on Monday, killing five people and wounding 15, police and officials said.

The large explosion damaged the building and destroyed or damaged several vehicles at the main gate of the compound belonging to a police rapid reaction unit. All of the casualties were police personnel.

"The blast was caused by a suicide car bomber who tried to ram into the building of the brigade, the 2nd rapid reaction brigade. He tried to ram into the building but policemen at the reception deterred him, forcing him to blow up the car at the entrance when they denied him the chance to go inside,"Ali Ghanem al-Maliki, the head of the Basra provincial council security committee told Reuters.

At least four bodies were brought to a local hospital, health officials said.

Basra, which handles the bulk of Iraq's oil exports, has generally seen less attacks this year than other cities in the country following an overall decline in levels of violence since the peak of sectarian conflict in Iraq in 2006-2007.

Earlier this month, a bomb attack against an oil storage depot near the Zubair oil field in Basra set one oil storage tank ablaze, but caused no casualties.

The last major attack in Basra occurred in March, when a roadside bomb targeting a US military convoy exploded near a civilian bus, killing six people and wounding a dozen others.

US and Iraqi military officials say they believe attacks may rise ahead of a year-end deadline for the withdrawal of the last remaining US troops in Iraq, although Iraqi Prime Minister Nouri al-Maliki is considering requesting that some US military stay on in a training and advisory role.