SANAA - The World Health Organization (WHO) announced on Monday that the first flight carrying Yemeni patients in critical need of treatment left the country's rebel-held capital Sanaa.

According to the WHO, the UN-marked plane bound for Amman, with eight patients and their relatives onboard, took off from the Houthi-controlled airport of Sanaa, which has been closed to commercial flights since 2016.

The WHO posted a statement on Twitter saying that "As part of the UN's medical airbridge operation, the patients will receive life-saving specialized care not available in Yemen."

"The majority of the patients are women and children who suffer from conditions such as aggressive forms of cancer and brain tumors, or who need organ transplants and reconstructive surgeries. The flights offer them a lifeline to receive the treatment they need to survive," said the statement.

The WHO confirmed that the medical operation is expected to continue with another three flights this week, bound for Amman and Cairo, carrying a total of 30 patients.

On Sunday, the United Nations Special Envoy to Yemen Martin Griffiths arrived in the rebel-held capital Sanaa to facilitate the humanitarian "medical airbridge".

Yemen's airspace has been controlled by the Saudi-led coalition since its intervention in the Yemeni conflict in March 2015 to support the internationally-recognized government of President Abd-Rabbu Mansour Hadi.

Yemen has been mired in a civil war since late 2014, when the Iran-backed Houthis seized control of much of the country's north and forced the Saudi-backed government of Hadi out of Sanaa.