Newborn conjoined twins were evacuated from a Syrian rebel stronghold to the capital, Damascus, after lengthy negotiations earlier this month.

But brothers Moaz and Nawras died early Wednesday before they could be transferred to a hospital outside Syria for urgent heart surgery. It's a tragic end to a story that was the subject of an international campaign to save their lives.

As we reported, the babies, who were joined at the chest, were born in the besieged area of Eastern Ghouta on July 23. Their hearts shared a sac, according to the BBC. The World Health Organization says it took days of negotiations to evacuate them. The hospital in Eastern Ghouta was short of supplies and unable to perform the surgery needed to separate them.

The Syrian Arab Red Crescent said in a press release that Moaz and Nawras died of heart failure. The organization says the pair had been accepted to a hospital in Rome, and "all formal leave approvals were signed in order to travel."

Hospitals in the U.S. and Saudi Arabia had also offered to treat the twins, as NPR's Allison Meuse reported.

Mona Kurdy, a spokeswoman for the Red Crescent, told The Wall Street Journal that "approval for the twins to leave Syria was granted Monday, but by then their condition had already started to worsen."

"There is no one who wasn't cooperative," Kurdy said, according to the Journal.

However, Mohamad Katoub, advocacy manager for the Syrian American Medical Society, told the Journal that Syria's Foreign Ministry was responsible for the ultimately fatal delays. The ministry was " 'looking for a medical solution that matched its political interests' and trying to secure medical treatment for the twins in a country with friendlier relations with Syria," he said.

Khatoub tweeted a portrait of the twins by Syrian artist Akram Abo Alfoz:

SAMS also said in a statement that the Red Crescent "kept Moaz and Nawras at a private hospital in Damascus for almost two weeks despite the urgency of the case" without releasing any information, which it says "hindered the evacuation process."

SAMS led the international effort to evacuate the twins, drawing attention to their plight and eliciting a message of support from U.S. Ambassador to the U.N. Samantha Power.

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