At least five people have been killed and 20 wounded in a series of blasts in and around the capital Baghdad, police officials have said.

The first attack happened on Sunday near a police station in the suburb of Radwaniya, southwest of the city.

Police also reported a roadside bombing on a commercial street in the Hay Jami'a neighbourhood, which killed three people and wounded nine.

Near Baghdad International Airport, officers say a car bomb tore through a car park at one of the checkpoints leading to the airport, wounding five people and causing extensive damage to vehicles.

In another incident near the airport, a suicide car bomb attack targeted a UN convoy, causing no injuries among UN staff, a UN statement and security officials said.

The UN said the three-vehicle convoy was hit by an explosion as it travelled from the airport to Baghdad's highly-fortified Green Zone, where its headquarters are located.

"No UN personnel were killed or injured in the incident and all proceeded safely back to the UN compound. One of the vehicles sustained serious damage," the statement said.

UN Iraq envoy Nickolay Mladenov said: "The unfortunate incident this morning will not deter the UN from continuing its work in support of Iraq and its people, who have lived with violence for too long."

Meanwhile, Iraqi forces appeared close to retaking the country's biggest oil refinery near the city of Beiji from the ISIL armed group on Saturday.

ISIL fighters had seized Beiji and surrounded the nearby refinery in June during a lightning campaign through northern Iraq.

Al Jazeera