Doctors in Saudi Arabia have successfully separated conjoined twins from Yemen after a “difficult” 15-hour operation, Saudi state media said on Monday

The baby boys, Yussef and Yassin, were “conjoined in various organs,” according to the Saudi Press Agency (SPA). The operation to separate them needed 24 doctors.

Yemen has been plagued by a vicious seven-year conflict pitting the Saudi-backed government against Iran-backed Huthi rebels, whose seizing of the capital Sanaa in 2014 triggered an intervention by a Saudi-led military coalition.

More than 150,000 people have died in the violence and the country’s health system has been devastated, in what the United Nations describes as the world’s worst humanitarian crisis.

Saudi Arabia’s state-run King Salman Humanitarian Aid and Relief Center (KSRelief) regularly touts its humanitarian assistance to Yemen as evidence of Riyadh’s commitment to alleviating the suffering there.

The centre’s doctors carried out the “four-phase surgery” separating Yussef and Yassin, describing it as “among the most complicated” they had performed, the SPA said Monday.

Last July Saudi doctors separated a Yemeni baby from her parasitic twin, saying at the time it was their 50th successful operation on conjoined twins.

In December a separate set of Yemeni twins were separated by doctors in Jordan’s capital Amman before being flown back to Sanaa, according to the UN children’s agency.

According to the SPA, Saudi King Salman ordered the transport of yet another set of Yemeni conjoined twins, Mawaddah and Rahmah, to Riyadh “to undertake medical investigations and check on the potential” of separation.

According to the SPA article, the monarch “places a high value on the Saudi program for Siamese twins.”