The jihadists used light weapons and the cover of darkness to target the Hashed east of Tikrit, the capital of Iraq's Salahaddin province, two days after a twin suicide attack claimed by the group killed 32 people in Baghdad.

"IS launched an attack on the Hashed's Brigade 22," said one of the unit's officers Abu Ali al-Maliki.

Maliki told AFP the brigade commander was among those killed before reinforcements from the federal police came to the unit's aid.

Hashed security sources said the total toll was 11 dead and 10 wounded.

There was no immediate claim of responsibility, but security sources interviewed by AFP blamed IS.

Local and Western sources have expressed concern over the readiness of Iraq's security forces, who have been worn down by the spread of Covid-19, political infighting and corruption.

This week's attacks may be more illustrative of those accumulated shortfalls than any significant IS comeback.

Iraq declared the group territorially defeated in late 2017, but has continued to battle extremist sleeper cells, mostly in the country's mountainous or desert areas.