SANAA (Reuters) - Conjoined twin boys born in Yemen are in urgent need of treatment abroad, but are unable to leave because the war there has closed the capital city’s airport.

Doctors treating two-week-old Abd al-Khaleq and Abd al-Rahim said Yemen’s war-ravaged health system cannot keep them alive, and the parents are poor.

“They need to travel immediately. They will not be able to survive in Yemen under the social, political and economic circumstances in this country,” Doctor Faisal al-Balbali told Reuters in al-Thawra hospital in the capital Sanaa where the boys were born.

The tiny boys, who are being helped to breathe in an incubator, have separate heads.

Within their shared torso they have separate spines, lungs, hearts and digestive systems, but they share a liver, reproductive organs and pair of kidneys, arms and legs between them.

“Even if one is unwell, the other is fine ... They are different in every aspect,” al-Balbali said.

The doctors are appealing to the United Nations and international humanitarian organizations to arrange for the boys’ transfer abroad.

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Their parents were not present when the doctors were speaking about their sons, but medical staff said they had agreed with them to invite the media to highlight their plight.

Al-Balbali, head of the neonatal unit, said medics were not able to perform even basic diagnostic tests such as an MRI scan in Yemen, and certainly did not have the capabilities to separate them, if needed.

“This is a rare case,” said Doctor Abd al-Hakim Abu Taleb, the hospital’s general manager, who is writing up a report about their birth for doctors worldwide to study.

He said hospitals in Yemen have seen an increase in birth defects in recent years, something he said could be down to war conditions causing poor nutrition and lack of medicines.

Yemen’s almost four-year war pits the Iran-aligned Houthi movement against a Saudi-backed coalition trying to restore the government of Abd-Rabbu Mansour Hadi after it was ousted from power in Sanaa by the Houthis in 2014.

The conflict has killed tens of thousands of people, collapsed the economy and brought millions of people to the brink of famine.

Sanaa, where the boys were born in what the doctors said was a “complicated” birth for the mother, is under Houthi control.

The airport has been closed to civilian flights since 2015 because the Saudi-led coalition has control over Yemeni airspace. Only U.N. planes can land there currently and re-opening the airport is a key aim of U.N.-led peace talks which began with negotiations in Stockholm in December.