The last of a group of European workers who languished at a construction site in Baghdad's heavily-fortified Green Zone for months without pay went home on Friday, a migration official said.

The final group, comprised of 15 Ukrainians and seven Bulgarians, received a fraction of their agreed pay, but signed over power of attorney to an Iraqi lawyer who will file a lawsuit on their behalf against the company that hired them, and the firm that was in charge of the project on which they were working.

"The Bulgarians left this morning," Livia Styp-Rekowska, an official at the International Organization for Migration (IOM), said in an e-mail. "They are flying from Baghdad to Istanbul and from there to Sofia."

Styp-Rekowska said the Ukrainian nationals had already arrived in Kiev, where they were met by an IOM official.

"They were of course thrilled to leave," she said of the workers.

She said the Ukrainians each received $2,000 (1,460 euros) from the Iraqi foreign ministry as compensation, and the cost of their travel home was covered by Kiev's mission to Baghdad.

The Bulgarians were given $1,000, with the remaining $1,000 put towards the cost of their travel home.

The group, which initially numbered several dozen, first came to Iraq at the beginning of the year with promises of salaries of between $2,000 to $2,500 per month to construct villas for an Arab League summit that was initially due for March, but later postponed indefinitely.

The sub-contractor that hired them absconded with funds, and the firm that was awarded the contract to build the villas insisted it was not responsible for their salaries.

None has been paid since January. In April, they stopped working and want a total of around $300,000 in back pay. Food and other basic supplies were provided by the IOM and a private security contractor in the Green Zone.

Tens of thousands of foreign workers from around the world are toiling in post-war Iraq, which has a labour code and immigration law. But with Iraq's multitude of problems there is little monitoring, leaving migrants vulnerable and often exploited.