Renewed battles between government forces and Iran-aligned Houthi militias over the strategic city of Marib in northern Yemen have left 47 dead, including 16 pro-government forces, military sources said Saturday.

The Iran-backed militias are seeking to seize control of Marib and its surrounding oil fields, the Yemeni government’s last stronghold in the north after six years of fighting that has plunged the country into a humanitarian crisis.

Diplomatic efforts to secure a ceasefire in Yemen had intensified, in parallel with the fierce battle for the control of Marib, which has left thousands dead on both sides.

But with no agreement in sight, the fighting has flared again after a lull over the past month.

Sources with the internationally-recognised government said that 16 soldiers from their ranks were killed, including six officers, on Saturday. The insurgents rarely report their casualties.

The Houthis “launched attacks on various fronts, in an attempt to advance, but they were mostly repelled,” one of the officials said.

The sources said that warplanes from the Saudi-led coalition, which supports the beleaguered government, launched air strikes on militias’ sites.

The Houthis said on their Al Masirah television channel that the coalition had also carried out 17 air strikes in different parts of Marib province.

The fight for Marib threatens to escalate the wider war and has stirred international outcry because the city houses over a million displaced persons, many of whom live in camps on the outskirts of the city.

Houthi missile and explosives-laden drone attacks have hit residential and civilian areas inside the city itself. Earlier this month, they hit a petrol station, killing a total of 20 people, including children, according to Liz Theissen, a spokeswoman for the UN High Commissioner for Human Rights.

— Diplomatic failure —

The renewed fighting over Marib comes after the failure of a diplomatic push by the United Nations, the United States and regional nations to secure a ceasefire in Yemen.

The outgoing UN envoy for Yemen Martin Griffiths on Tuesday told the Security Council his own efforts over the past three years to end the war have been “in vain.”

“It is with deep regret that I report today that the parties have not overcome their differences,” he said.

Yemen has been devastated by the civil war which broke out in 2014, and millions of civilians are on the brink of famine, according to the UN.

The Houthis have repeatedly demanded the re-opening of the airport in the militias-held northern capital of Sana’a before agreeing to any ceasefire.

As well as the bloody offensive in Marib, the Houthis have also stepped up drone and missile strikes on Saudi targets, including its oil facilities.

Saudi air defences on Saturday intercepted and destroyed 11 drones fired at the kingdom by Houthis in Yemen, Saudi state media reported, quoting the coalition battling the militias.

“The interception operations were successful,” the coalition said in a statement, adding that the drones were packed with explosives and seven were neutralised in Yemeni airspace.