At least 1075 people were killed in Iraq from June 5 to 22, UN estimates reveal as the country has plunged into a conflict between the government and Islamist-led fighters.

UN human rights office spokesman Rupert Colville elaborated the numbers "should be viewed very much as a minimum," the BBC quoted him as saying.

The toll included summary executions and extra-judicial killings of civilians, policemen and soldiers who refused to take part in the conflict.

In unrest-torn provinces of Nineveh, Diyala and Salahuddin, where are insurgents controlled by the Islamic State in Iraq and the Levant (ISIS) are highly active, violence took 757 lives.

Another 318 lost their lives in the Iraqi capital Baghdad and southern Iraq, according to a UN report shown Tuesday in Geneva.

Baghdad is a key goal for ISIS, which wants to take it over and include it into a Sharia-ruled Islamist enclave carved out of territories held in Iraq and neighboring Syria.

The US and other states are trying to convince Iraqi politicians, including Prime Minister Nouri Al-Maliki and his Shia-dominated government, to urgently forge a coalition of national unity also comprising representatives of Sunnis and Kurds.

Over the past 24 hours ISIS has claimed full control of the country's biggest oil refinery at Baiji and has also announced it controls vast parts of Iraq's borders with Syria.