At least 30 people were killed in air strikes by a Saudi-led coalition on a Houthi-held security compound in northern Yemen on Monday, medical sources and officials said, one year after the rebels seized control of the country’s capital, Sanaa.

Thousands of Houthi supporters gathered in Sanaa to celebrate the anniversary, despite relentless air strikes by the Saudi-led coalition.

Gulf Arab forces and supporters of exiled President Abd-Rabbu Mansour Hadi, meanwhile, appear to be making scant progress in a ground offensive in the central desert against battle-hardened Houthi forces.

The coalition intervened in Yemen in March to restore Hadi after he fled to Saudi Arabia when the Houthis, backed by supporters of former president Ali Abdullah Saleh, overran his southern stronghold of Aden.

A coalition jet fired a missile on Monday into police headquarters in the al-Shaghadreh district of the northern province of Hajjah, northwest of Sanaa, that is in the hands of the Iranian-allied Houthis, regional officials said.

A second missile crashed at the compound as rescue teams and residents arrived, causing a large number of casualties including at least 30 dead, according to medics on the scene.

Earlier in the day, coalition warplanes bombed a cement factory at Ibs, another Hajjah district. Local officials said the strike happened before workers arrived for work, but three shepherds who happened to be tending flocks nearby died.

Almost daily air raids by Saudi-led forces have escalated since the Houthis fired a land-to-land missile at a coalition base in central Marib province two weeks ago, killing more than 60 soldiers, most of them from the United Arab Emirates (UAE).

The UAE pledged to push ahead with the coalition offensive to dislodge the Houthis - seen by US-allied Gulf Sunni Muslim as a proxy for would-be Iranian expansionism in the Arabian Peninsula - from Sanaa. The Houthis deny such links and say they are waging war against corruption and misrule in Yemen.

International human rights groups have voiced concern at the growing number of civilians killed in the intensifying air war.

Coalition officials said a major westwards thrust against the Houthis in oil-producing Marib began last week, and local media have since reported advances in the region.

A regional official in Marib said on Monday that the battlefronts had been quiet since the Arab coalition spearheaded by UAE forces completed “securing” the environs of Marib city.

On Sunday, an air strike targeted a market in the Mnabbeh district of the northern province of Saada, the historical Houthi bastion, killing at least 20 people and injuring over 70.

More than 4,500 people have been killed in bloodshed since the Saudi-led intervention, according to United Nations figures.

(FRANCE 24 with AFP and REUTERS)