Forty Indian citizens working for a Turkish construction company near the Iraqi town of Mosul have been kidnapped, India's Foreign Ministry reported Wednesday, according to Reuters.

Ministry spokesman Syed Akbaruddin said there had been no contact with the kidnappers and no ransom demand had been received, Reuters reported. It was not immediately clear when the Indian workers were abducted.

Over the past week, militants have overrun Mosul and seized wide swathes of territory as they stormed toward the Iraqi capital of Baghdad, according to Reuters.

Akbaruddin said they were mostly from northern Indian states including Punjab, and had been working for the Tariq Noor al-Huda construction company in Iraq, Reuters reported.

Relatives in the Punjabi city of Amritsar said they had received phone calls from some of the Indian workers on Sunday, five days after Mosul was captured, according to Reuters.

There are about 10,000 Indian citizens working and living in Iraq, but only about 100 are in violent, insecure areas, Foreign Ministry spokesman Akbaruddin said, Reuters reported. They have all been advised to avoid traveling by road.

"We are willing to assist any of the nurses who wish to return to India," Akbaruddin said, adding that "several Indian nurses prefer to stay back" in Iraq, according to Reuters.

India sent a senior diplomat to Baghdad on Wednesday, and planned to bring back some citizens on Friday, Reuters reported. The government also opened a call center to take phone calls from worried families with relatives in Iraq. By Wednesday afternoon, it had received 60 calls, he said.

National TV station NDTV broadcast a recording of a phone call with one of the nurses in Tikrit on Tuesday, according to Reuters.

"We are afraid. We have no security here," a woman identified as nurse Marina Jose said over a crackling phone connection, Reuters reported. "All the military, police, everybody escaped from here. Only we are here."

On Wednesday, Iraq's prime minister said Iraqi troops had launched a counteroffensive as the fighters, led by the al-Qaida breakaway group Islamic State of Iraq and the Levant, laid siege to the country's main oil refinery, according to Reuters.