Simba the lion and Lula the bear, the ailing last two residents of Mosul zoo, were flown out of Iraq Monday to receive emergency care from an animal welfare group.

A group of veterinarians from the Four Paws International charity took the animals out of war-battered Mosul and after many administrative delays finally managed to fly them out to Jordan from the Iraqi Kurdish capital of Arbil.

"We're in the plane with the animals, we're leaving now," said Amir Khalil, a 52-year-old Egyptian-Austrian vet who headed the Four Paws mission.

The doctor found the pair covered in dirt and excrement in February, abandoned in their cages at the privately owned zoo in the eastern half of Mosul.

Iraqi forces launched a massive operation to retake the city, Iraq's second largest, from the Islamic State group in October and spent weeks battling the jihadists street by street before eventually retaking the east bank in January.

When Four Paws reached the zoo, nobody had entered the cages in weeks and no other animals apart from the female bear and the male lion had survived.

When Khalil and his team came back to the region in late March, they had one goal which was to remove the animals temporarily from Iraq so they could receive proper veterinary care.

- 'Most complicated mission' -

"I'm a vet -- I have to look after these animals," said Khalil, a kind of "roving war zone veterinarian".

"They are refugees. It's our duty to take them to a sanctuary."

It was supposed to be a formality, but it took Khalil and his team two weeks to finally squeeze the right paperwork out of the administrative confusion that prevails in post-jihadist Mosul.

In late March, Khalil had put the two beasts to sleep, taken them out of their filthy cages on stretchers and loaded them aboard a truck using a crane, hoping to be on an aircraft in a matter of hours.

The thud of artillery fire across the river was a reminder than while eastern Mosul had been fully reconquered by the federal forces, the area was still a war zone.

As the animal welfare team cautiously extracted the animals from the abandoned zoo, Ahmed Manhel looked on.

"I wouldn't mind receiving some care myself," the 18-year-old had said, leaning on two wooden crutches.

He lost his right leg in an explosion in November.

"I need to leave this place, I need a prosthetic leg," the young Iraqi said, moments before the truck carrying the animals departed for Arbil.

The truck was stopped at a checkpoint, however, and a second evacuation attempt the following day also failed.

The two animals remained on a dusty roadside for nine days before the necessary permits were secured.

The lion developed a respiratory problem as a result of the delay.

"This has probably been our most complicated mission," said Yavor Gechev, from the Four Paws group which has done similar work in the Gaza Strip, in Egypt during the Arab Spring and in Libya.

Before the plane finally took off, doctor Khalil was relieved.

"This is the beginning of a new life for the animals," he told AFP. "From now on, they won't have to be part of this war."