Cairo: UN envoy for Yemen Martin Griffiths has intensified his efforts to revive Yemen’s stalled peace process through shuttle diplomacy with the country’s warring sides.

He met Yemeni Vice President Ali Mohsen and Prime Minister Ahmad bin Daghr in Riyadh on Wednesday. Later, Griffiths flew into Muscat where he reviewed with Omani Foreign Minister Yousuf Bin Alawi the latest developments in Yemen.

Griffiths earlier met leaders from Iran-allied Al Houthi movement that toppled the internationally recognised government in late 2014, triggering a devastating war.

His current efforts come more than a month after Al Houthis failed to appear in Switzerland for UN-sponsored indirect talks with the Saudi-backed government.

Moshen voiced appreciation for Griffiths’ peacemaking efforts and accused Al Houthi militants of continuing their “oppressive” policies against civilians, Yemen’s official news agency reported.

Three civilians were killed when Al Houthi militiamen shelled an ambulance south of the embattled coastal city of Hodeida in western Yemen, Al Arabiya reported Thursday.

A 60-year-old woman was also killed by Al Houthi shelling of her house south of the south-western province of Taiz, the station added, citing military sources.

The Yemeni army condemned the attacks, saying they mark a “dangerous development” in Al Houthi attacks on civilians after the extremists’ recent military setbacks in the country.

Foreign donors and international aid groups in Yemen remain focused on the dire humanitarian needs in the Arab world’s poorest nation. War has pushed Yemen, a country of 28 million people, to the brink of famine and fuelled a deadly cholera epidemic.

The United Arab Emirates is refurbishing hospitals and classrooms, and has provided millions of dollars in aid.