At least five people were killed and 18 injured in a series of explosions in the Iraqi oil city of Kirkuk, medical sources in the city's general hospital said on Thursday. Xinhua News reports 20 injured.

At least six improvised explosive devices went off in three main streets in Kirkuk, some 250 kilometers north of the Iraqi capital Baghdad, and two more explosive devices were defused by security forces, the media office of the Joint Operations Command said in a statement.   

The statement gave a death toll of three people and said 16 others were wounded.

Ammar al-Jubouri from the Kirkuk provincial police told Xinhua that a policeman was among the killed and four others among the injured.

The explosion sites included two malls, an ice cream shop and a butcher's shop, local media reported.

The security forces sealed off all the roads leading to the sites of the explosions and immediately launched an investigation into the blasts.

Al-Jubouri added that the security forces are looking for two cars allegedly seen planting the bombs in the streets.

For years, tension has been running high in the ethnically mixed city of Kirkuk, which has distinct ethnic groups, including Kurds, Iraqi Turkmen, Arabs, and Assyrians, who all lay conflicting claims to this zone, and all have their historical accounts and memories to support their claims.

No group has so far claimed responsibility for the attacks. 

The security situation in Iraq was improved after former Iraqi Prime Minister Haider al-Abadi declared victory over ISIL in December 2017, but ISIL remnants have since melted in urban areas or resorted to deserts and rugged areas, carrying out guerilla attacks against security forces and civilians.

Aside from ISIL remnants, Iraq continues facing severe challenges including resolving the political, sectarian and tribal conflicts that fueled the spread of extremism and its entanglement in regional rivalries. 

(With input from Xinhua and Reuters)