Sana’a: The Saudi-led coalition fighting Iran-backed Al Houthi militants in Yemen suspended its air war Monday to allow desperately needed aid deliveries, but clashes persisted in several areas on the ground, witnesses said.

Al Houthi militants, who control swathes of the country, including the capital Sana’a, said they had not been consulted about the unilateral coalition ceasefire that began at midnight (Sunday 2100 GMT).

The Arab regional coalition, which has waged four months of air strikes in support of exiled President Abd Rabbo Mansour Hadi, announced the five-day truce to allow emergency supplies to flow into the impoverished nation.

It reserved the right to respond to “military activity or movement” but there were no reports of new air raids by dawn despite several new attacks by Al Houthi militants.

Al Houthis bombarded areas overnight in the southern provinces of Taiz, Lahj and Dhaleh, according to witnesses and military sources.

Militant tanks fired on residential areas in Jebel Sabr in Taiz, witnesses said, sparking clashes with loyalist troops that caused an unknown number of deaths on both sides, witnesses said.

In Marib to the east of the capital Sana’a, fighting broke out before dawn when Al Houthi militants launched an offensive against loyalist positions, residents said.

UN chief Ban Ki-moon earlier made a plea for all sides to “agree to and maintain the humanitarian pause for the sake of all the Yemeni people”.

But Mohammad Ali Al Houthi, the self-described “president of the High Committee of the Revolution”, a body formed by Al Houthi militants, said in comments published by the militant-controlled Saba news agency Sunday that his group had not been consulted by the UN about the ceasefire.

The group could therefore not give a “negative or positive” answer about the truce, he said.

The United Nations says the conflict has killed more than 3,640 people, around half of them civilians, since late March.

A UN-declared six-day truce failed to take hold earlier this month after it was ignored by both the coalition and Al Houthi militants.

Relief supplies, however, have recently begun to trickle into Aden after loyalist fighters secured the southern port city, which had been Hadi’s last refuge before he fled to Saudi Arabia in March.

Several ships have docked in Aden since Tuesday carrying thousands of tonnes of aid supplies sent by the UN World Food Programme (WFP) and Gulf nations but distributing the aid, particularly outside the city, presents a major challenge.