ISIS and Iraq's oil: Lucrative resource eyed
Foreign staff working at the power plant in Baiji in northern Iraq were evacuated just hours before jihadists from the extremist organisation ISIS and other Sunni militants launched their attack on the nearby refinery on Tuesday night.
The foreigners were flown to safety in helicopters with help from Iraqi special forces.
The BBC understands they had not been able to leave earlier because the security forces had not allowed them to travel on the road heading north.
A small group of British workers was among those forced to leave Baiji over the past seven days.
The Iraqi authorities deny that the militants are in control of the Baiji refinery. They say they have killed 44 militants and retain control of the refinery.
The refinery, which is now shut down, supplies a quarter of the country's refining capacity and is critical for Iraq's supplies of petrol and other petroleum products.
And the power plant is equally important, as the country still suffers from acute shortages of electricity.
It was always likely the militants would target Baiji.
The area is dominated by Sunni Muslims and was a hotbed of insurgent activity during the US occupation, making it fertile ground for ISIS.
And ISIS has a track-record of seizing lucrative assets such as refineries.
"ISIS is expert at monetising refining operations," says Mike Knights, a fellow at the Washington Institute. "They have a couple of refineries in Syria and even sell some of the oil to the Syrian government."
The war chest which ISIS has built up from its operations in recent years would appear to make it the worlds' richest militant Islamist organisation.
A senior source in the Iraqi government has told the BBC that ISIS is believed to have $2bn (£1.2bn) in cash and assets.
The information comes from detailed financial documents found on computer memory sticks that were recently seized by Iraqi security forces from ISIS members.
Much of the money comes from its operations in Syria where it controls areas in the north.
But its recent offensive in northern Iraq is also believed to have been extremely lucrative, giving it access to cash held in major banks in Mosul and other towns and cities which it has seized.
It is also believed to have looted large amounts of military equipment from Iraqi bases.
There are reports of US-supplied Humvee armoured vehicles being driven across the border into Syria by the jihadists.
The Iraqi government source also told the BBC they had found the names of foreign fighters who had joined ISIS on the memory sticks and the initials of people working in government ministries in Baghdad who were supplying information to the group.
A mixture of extreme ruthlessness and vast resources giving it the ability to carry out numerous attacks in different areas goes some way to explaining the rapid advance ISIS has made through the Sunni regions of Iraq in recent weeks.
But now as its fighters reach the outer limits of the Sunni areas, what is less clear is whether it does have the capability to push into the capital Baghdad, which has a large Shia population.
The Iraqi army and Shia militias have been bolstered recently by new recruits and fired up by the call to arms made by Iraq's most senior Shia religious leader, Grand Ayatollah Ali al-Sistani.
Last week he called on everyone capable of carrying a weapon to go and fight; these volunteers have been moving to the frontlines north of the capital.
In a televised address to the nation on Wednesday, Prime Minister Nouri Maliki tried to boost morale, saying the crisis had made the country more united and that the militants would be confronted and defeated.
The coming weeks will be critical for his future and that of his country.