* Ceasefire aimed at preventing humanitarian disaster
* Violence dwindles, scattered incidents reported
* Six weeks of fighting leaves Aden battered (adds quotes, figures on Aden)
By Mohammed Ghobari and Mohammed Mukhashaf
CAIRO/ADEN, May 13 (Reuters) - A five-day truce in Yemen appeared to be broadly holding on Wednesday, despite reports of air strikes overnight by Saudi-led forces and continued military activity by the country's dominant Iranian-allied Houthi group.
Witnesses in the southwestern city of Abyan said warplanes had hit positions there after the Houthi seized the area following the start late on Tuesday of the ceasefire, which is intended to ward off a humanitarian catastrophe.
Residents of the southern provinces of Shabwa and Lahj, which have witnessed heavy ground clashes between local militiamen and the Houthis, also reported air strikes overnight.
At least 35 civilians were killed by the Saudi-led attacks on the cities of Abs and Zabeed in western Yemen on Tuesday, residents said, before the beginning of the ceasefire.
Seeking to restore exiled President Abd-Rabbu Mansour Hadi, an alliance of Gulf Arab nations has since March 26 been bombing Houthi militia and allied army units that control much of Yemen.
In the bulwark of opposition to the Houthis in the southern city of Aden, the scale of over six weeks of clashes emerged.
Over 600 people had been killed and 3,000 had been wounded, while 22,000 residents had been displaced since the Houthis first pushed into the city on March 25, local watchdog group, the Aden Centre for Monitoring, said on Wednesday.
Residents expressed doubts that the break in fighting, which paused round-the-clock gunfire that had defined Aden life in recent weeks, would last.
"Aden needs a humanitarian truce so badly, given the lack of food, fuel and everything else. But we question the intentions of the Houthis and believe they will take advantage of the truce to take more areas," resident Hassan al-Jamal said.
Saudi Arabia and its Sunni Muslim allies believe the Houthis are a proxy for the influence of their arch-rival, Shi'ite Iran, in a regional power struggle that has helped exacerbate sectarian tensions across the Middle East.
AID AND MEDICINE
Saudi state television quoted an official source at the Defence Ministry as saying projectiles had fallen on the Najran and Jizan areas on Wednesday morning and that some sniper fire by the Houthis had been detected. There were no casualties.
"The position adopted by the armed forces was to exercise restraint, abiding by the humanitarian truce approved by the coalition forces," the television quoted the official as saying.
There was no immediate confirmation of the accusations by Saudi media.
The truce is meant to allow in aid and medicine to Yemen, where the United Nations believes 828 civilians, including 182 children, have been killed since March 26. There was no word of any new aid arriving by Wednesday afternoon.
The scattered reports of incidents would suggest violence at a far lower level than before the truce formally began.
The Houthi TV channel al-Masira said Saudi ground forces shelled their northern stronghold province of Saada and called the bombings a violation of the ceasefire.
The Saudi state news agency SPA said King Salman, at a royal court ceremony attended by President Hadi and Yemeni Prime Minister Khaled Bahah, authorised the laying of the foundation stone for a humanitarian relief centre.
The Saudi-owned al-Arabiya channel said the monarch had allocated one billion riyals ($265 million) to the Yemen relief work, in additional to a similar amount he had pledged earlier. (Reporting by Mohammed Ghobari; additional reporting by Omar Fahmy in Cairo, Writing by Noah Browning, editing by Sami Aboudi and Crispian Balmer)