Tunisia's governing Islamist Ennahda Party has agreed to resign in favour of a caretaker government to resolve a political crisis that has paralysed the country.

The assassination of left-wing politician Mohamed Brahmi at the end of July, the second such killing in five months, was a turning point for the country's opposition, which pulled its deputies out of parliament and staged a string of protests across the country.

The opposition damned the governing party for ignoring a rising trend of Islamist radicalism.

Tunisia kicked off the so-called Arab Spring by overthrowing its long-ruling dictator, Zine el-Abidine ben Ali, but it has been dogged by terrorist attacks, a struggling economy and widening divisions between Ennahda and the opposition.

After the assassination of Mr Brahmi, half-million strong trade union UGTT mediated between the government and opposition for months to attempt to resolve the deadlock.

"It is a positive development. Ennahda has accepted the plan without reserve or conditions," said UGGT deputy head Bouali Mbarki on Saturday.

He said his union had obtained a written statement from Ennahda and opposition officials also confirmed the agreement.

Prime Minister Ali Larayedh's government will resign in three weeks.

A neutral figure will head an interim, non-partisan government.

Meanwhile, MPs boycotting the assembly will return to finish the constitution over the next four weeks.

An election commission will be set up to organise elections in coming months.