SANAA, Dec. 26 (Xinhua) -- The negotiation over the release of 13 UN staff arrested by the Houthi group in the Yemeni capital Sanaa concluded on Thursday, Director-General of the World Health Organization (WHO) Tedros Adhanom Ghebreyesus said in a statement.

"We continue to call for the detainees' immediate release," Ghebreyesus wrote on social media platform X.

The UN confirmed in June that 13 of its staff members have been detained by the Houthis in Sanaa. The militant group has accused those arrested UN staffers of involving in espionage acts for the United States.

In the meantime, Ghebreyesus noted that the Sanaa International Airport came under aerial bombardment as he and some other UN and WHO officials were about to board their flight from Yemen's capital Sanaa.

"One of our plane's crew members was injured. At least two people were reported killed at the airport. The air traffic control tower, the departure lounge -- just a few meters from where we were -- and the runway were damaged," he said.

Noting that he and his colleagues are safe, the WHO chief said they will need to wait for the damage to the airport to be repaired before they can leave.

Israel vowed on Thursday to kill Houthi leaders and dismantle the group's military power shortly after it launched "intelligence-based" airstrikes targeting Houthi-controlled military targets on Yemen's western coast and inland Yemen.

The Houthis, who control much of northern Yemen, have been launching regular rocket and drone attacks against Israel and disrupting "Israeli-linked" shipping in the Red Sea since November 2023 to show solidarity with Palestinians in Gaza amid their conflict with Israelis. ■