Bombs and mortars rock Iraq's restive city of Kirkuk

At least 11 people have been injured in a series of bombings in Kirkuk, when militants launched new attacks on the troubled Iraqi city on Wednesday.

Police told Reuters that the roadside bombs and mortars targeted a commercial district in Kirkuk, in the latest attacks by suspected Islamic State group militants on the oil-rich northern Iraq city.

Anadolu news agency reported that four explosives were detonated, including one on the Baghdad road, but made no mention of mortar rounds.

Police sources told the Turkish news agencies that they didn't know who was behind the attack.

Hours earlier, Iraqi security forces in Kirkuk province arrested three suspected militants including one they said was an IS intelligence official.

A day earlier, an Iraqi commander was killed when a bomb targeted a military convoy in the province.

IS was defeated in Iraq last year, although sleeper cells have launched a series of attacks on military and civilian targets since then, as well as kidnappings.

Kirkuk has been one of the primary targets of the militants, with tight security in the capital Baghdad and Shia south making attacks there more difficult.

Kurdish forces took control of Kirkuk province in 2014, when a sweeping IS offensive saw Iraqi government forces flee south.

Following the defeat of IS, Iraq's military - including a coalition of mostly Shia militias - launched an offensive on the oil-rich city last year, forcing Kurdish fighters to evacuate.

Kirkuk is one of the most diverse cities in Iraq, with Arabs, Kurds and Turkmens inhabiting the area, but sectarian and ethnic divisions have been pronounced, particularly after the US-led 2003 invasion.