Saudi warplanes launched fresh air raids in central and eastern Yemen on Friday in an apparent bid to gain the edge ahead of a five-day ceasefire, which was due to come into effect at midnight.

A local security official said Houthi rebels amassed fighters on the outskirts of the strategic central city of Taiz, shelling several residential areas although there were no casualties.

The United Nations has brokered the truce to run until July 17, the end of the Muslim holy month of Ramadan. The pause in the fighting will allow aid to reach millions of Yememis on the brink of famine. It includes unhindered access to all parts of the country, including sea and airports.

Yemen has descended into chaos in recent months amid fighting between forces loyal to exiled President Abed Rabbo Mansour Hadi and Houthi rebels, backed by Iran. A Saudi-led coalition intervened in March, launching airstrikes on Houthi targets.

Friday's ceasefire comes after a similar deal in May was repeatedly violated and much of the aid never reached those who needed it most.

Saudi Arabia doubtful of cease-fire

Fears are growing that the new pact will also be ignored. A Saudi official told the AFP news agency that the five-day hiatus would be "useless," blaming a lack of "any evidence of commitment from the other party."

The cease-fire is further complicated in that Houthi rebels are not in full control of all of their allied forces.

But the UN says it has received assurances from Hadi and the Houthi rebels that they will respect the pause.

Aid agencies have described the latest truce as the "final hope" to reach areas of aid. The World Food Programme said two ships carrying food and fuel were waiting to dock off the coast of Aden.

The UN confirmed it would scale up operations during the cease-fire, aiming to reach around 13 million people who face food shortages. A desperate need for medicine and vaccinations in several areas has also been reported.

Charities plan to stockpile supplies throughout the country, including food for over a million people for a month, as a long-term solution remains a distant possibility.

More than 3,200 people have been killed since Saudi Arabia intervened, almost half of them civilians.

Riyadh has vowed that it won't stop airstrikes until Hadi - who is currently exiled in Saudi - has been reinstated.

AQAP calls for attacks on US

Separately on Friday, the new leader of al-Qaeda in the Peninsula (AQAP) called for attacks on the United States, according to a website representing the group.

Qassim al-Raymi took over following the death of Nasser Al Wuhayshi, who was killed in a US drone attack in Yemen's Hadhramaut region.

AQAP, which is Yemen's branch of the terrorism network, is also in the middle of a territorial grab for large parts of the country and is seen by US intelligence as the most lethal franchise of the terrorist organization.

mm/kms (AFP, dpa, Reuters)