The bodies of 39 Indian construction workers kidnapped in Iraq in 2014 by Isil have been found in a mass grave, India's foreign minister said Tuesday.

Sushma Swaraj told the upper house of parliament the workers had been murdered by the Islamic State of Iraq and the Levant (Isil).

Their bodies had been found in the grave in the village of Badush northwest of the city of Mosul and taken to a local organisation for DNA testing.

"Yesterday they told us that 38 samples had matched. The 39th had a partial match as he didn't have any immediate family," said Swaraj.

The workers were abducted in June 2014 when Isil jihadists overran large swathes of territory in Iraq and captured Mosul.

The government had for years insisted they were believed still alive and the latest announcement sparked criticism from some relatives of the dead.

The victims were mostly from poor families in India's northern state of Punjab and had been working for a construction company in Mosul when they were rounded up.

"We got to know that these people were moved from Mosul to Badush by their captors," Swaraj said.