IRAQI government troops have given up efforts to retake the city of Tikrit from Islamic State (Isis) forces, with no fighting reported this morning.

The army, supported by Shi’ite militia groups, launched an offensive a fortnight ago to recover the city seized by the Islamist group on June 12.

But the pro-government forces fell back to a base three miles south of the city on Tuesday evening after coming under concentrated mortar and sniper fire.

Tikrit is a stronghold of ex-army officers and Saddam Hussein loyalists who allied themselves with the Isis-led offensive last month.

The Iraqi military had attacked from the village of Awja, about five miles south of Tikrit and Tuesday’s initial fighting occurred in the south part of the city.

State soldiers retook Awja, the birthplace of Saddam, on July 3.

The setback for Baghdad coincided with Isis advances in north-eastern Syria and a call from UN secretary-general Ban Ki Moon for all countries, especially Iraq’s neighbours, “to come together and support Iraq in its fight against terrorism.”

Mr Ban urged Iraq’s leaders to unite behind a political process acceptable to all parties and form a new government “in the spirit of national unity and inclusiveness.”

He said said that reports of mass summary executions by Isis are “extremely disturbing” and its use of water as a weapon is a new and “dangerous trend.”

The group is said to have caused extensive flooding and cut off water supplies to parts of Iraq, having taken control of dams on the Euphrates river.