The Isis militants, who took effective control of vast swathes of northern Iraq and are closing in on the capital Baghdad after running through the weak defence of a disintegrating army, are busy setting up parallel governance structures in the cities they now control.

The militants have apparently reassured the safety of dozens of nurses from India who were trapped in a hospital in Tirkit and offered to pay their overdue salaries.

Days earlier, as many as 46 nurses had sent a desperate plea to the government of India saying they were in danger and wanted to be evacuated.

However, they have changed their minds and agreed to stay on in Tikrit, the Times of India reported. Tikrit had witnessed the horrible massacre of hundreds of air force recruits by the militants from the Islamic State in Iraq and the Levant (Isis).

One of the nurses told the Times of India the fighters were courteous to them and offered to pay their salaries and dues. The militants, who took control of the Tikrit Teaching Hospital in the hometown of former dictator Saddam Hussein, have asked them not to venture out of the hospital.

"For the moment we're safe in the hospital ... We hear gunfire but don't know what's going on," said Jency James, one of the nurses.

Though they had the basic necessities, the nurses said they still feared for their safety. "People from Red Cross bring us milk and water, which is a great relief," said Sona Joseph.

They also said Indian embassy officials were in touch with them but were not aware of the happenings outside, especially the kidnapping of 40 Indian construction workers in Mosul.

"The bombing has cut off our internet connections and we don't know how long our phones will work," one of them said.

Other reports too have confirmed the local administration has changed following the Isis militants' capture of Tikrit, but that the salaries of the hospital staff have been revised lower.

The IANS news agency said the nurses were now being offered a pay of just $200 a month compared with $750 per month given under the earlier contract.

Reports from Kerala state say the nurses who have agreed to stay back in Tikrit have few options. Most of them had taken huge loans to pay the recruitment agencies that hired them for overseas jobs.

"I have to pay back the loan. I don't know what I'm going to do ... It's like being caught in a death trap," said one of the nurses.