Violence in Iraq has reached its worst level since 2008, the UN mission to Baghdad has said, reporting that more than 8,800 Iraqis were killed in 2013.

The UN said 7,818 civilians died last year. The total including members of the Iraqi security forces surged to 8,868, with 759 people killed in December alone.

A report on Wednesday by Iraq Body Count, a British-based NGO, confirmed the trend, predicting that the coming year could be more bloody than the last. The NGO's own figures suggest 9,475 civilians were killed in 2013, compared with 10,130 in 2008.

The group said: "Al-Qaida in Iraq has found fertile ground in all this discontent and has attacked the Iraqi government …by killing members of its army, its police forces, its politicians and journalists, as well as its Shia population.

"The last six months have seen the massacres of entire families as they sleep or travel to a holy place, sometimes five, sometimes 12 family members at a time." It concludes: "The faults are now as wide and deep as trenches."

The spike in violence can be attributed to several factors, including the crackdown by Iraq's Shia-led government on a Sunni protest camp last April, in which 49 people were shot dead. These killings spawned numerous revenge attacks against Shia targets in Baghdad and across the rest of Iraq.

Amid discontent from Iraq's Sunni minority and Shia majority, the prime minister, Nouri al-Maliki, has in effect given up on cross-sectarian politics. He imprisoned high-profile Sunni politicians and forced others into exile.

Six bodyguards of a prominent Sunni protest leader, Ahmed al-Alwani, were killed in a shootout when security forces arrived to arrest him last week.

At the same time, al-Qaida in Iraq has spectacularly rebuilt itself. The Islamic State in Iraq and the Levant (Isis), a radical Sunni militia, has taken advantage of worsening sectarian tensions as well as the war in Syria. The group is highly active in Iraq's western and northern provinces. It is believed to be behind a wave of co-ordinated bomb attacks in Shia areas of the Iraqi capital.

The levels of violence are now comparable to the dark days of 2008, though back then the death toll was falling rather than rising. They are not as bad as 2006 and 2007 when the country came close to civil war. The resurgence has taken advantage of the departure of US forces in 2011 and an influx of foreign fighters.