The violence in Iraq has killed more than 5,500 civilians over the first six months of the year, according to a report by the United Nations that documents the massive humanitarian toll of the Sunni militant offensive.

The Islamic State (Isis) and other Sunni insurgents seized control of the city of Falluja, as well as part of nearby Ramadi in Anbar province in early January. The militants then launched an offensive in June that has brought a huge swath of northern and western Iraq under their control.

In its report, the UN mission to Iraq says at least 5,576 civilians were killed and another 11,665 wounded from 1 January until the end of June. Another 1.2 million have been driven from their homes by the violence, it adds.

The pace of civilian deaths over the first six months marked a sharp increase over the previous year. In all of 2013, the UN reported just over 7,800 civilians killed, which was the highest annual death toll in years.

The fighting "has inflicted untold hardship and suffering on the civilian population with large-scale killings, injuries, and destruction and damage of livelihoods and property", the UN report says.

It also documents human rights abuses by both sides of the conflict that may constitute crimes against humanity or war crimes.

The UN said Isis and its allies had committed "systematic and egregious violations" against civilians, including killings, sexual violence, kidnappings, destruction of property and attacks on places of religious worship.

It also documented violations by government forces, including summary executions of prisoners and detainees.

The UN urged all sides in the conflict to ensure the protection of civilians, and to respect international law and humanitarian law.

The office of the Iraqi president, Jalal Talabani, said on Friday the ailing leader would return on Saturday from Germany, where he has been receiving medical treatment since 2012. Few details have been released about his condition.

Talabani is finishing up his second consecutive term as president and is not eligible to run again.