The UN Security Council convened Tuesday to discuss the crisis in Yemen, amid growing concern over the deteriorating situation and calls for the parties to re-engage in the political process, diplomats said.

The meeting was held behind closed doors, at Britain's request.

Special envoy for Yemen Martin Griffiths, briefing the council via videoconference, "reiterated the importance of stopping the ongoing military escalation before it is too late," UN spokesman Stephane Dujarric said later.

"He warned that recent developments jeopardize the progress the parties had made on de-escalation and confidence building," the spokesman added.

The UN welcomed the Huthis' release earlier in the day in Sanaa of 64 children captured during military operations.

One diplomat, speaking on condition of anonymity, said the council would be issuing a statement urging the belligerents to return to the table and expressing its concern over the situation facing civilians. The UN has called it "the world's worst humanitarian crisis."

Members of the Yemeni Iran-backed Huthi rebels military police parade in the streets of the capital Sanaa on January 8, 2020
Members of the Yemeni Iran-backed Huthi rebels military police parade in the streets of the capital Sanaa on January 8, 2020 AFP / MOHAMMED HUWAIS

Earlier in Washington, US Secretary of State Mike Pompeo called on all parties to exercise restraint.

"The United States government is alarmed by renewed violence in Yemen," he said in a statement. "Renewed fighting is unacceptable and threatens to undermine this hard-earned progress.

"We call on all parties to put the needs of the Yemeni people first and immediately return to restraint. The Huthis must cease attacks on Saudi territory."

Clashes between the rebel Huthis and Yemeni government forces resumed on January 19 after months of relative calm.

On Saturday, the Huthis seized control of a strategic highway east of Sanaa, pursuing their offensive to the north and east of the Yemeni capital, according to loyalist military officers.

The war, which began in 2015, pits the Iranian-backed Huthi rebels against government forces backed by a Saudi-led military coalition.

The war has claimed tens of thousands of lives, most of them civilians, according to non-governmental groups.