SANAA (AFP) - Warplanes from the Saudi-led coalition hit Yemen rebel positions in the central city of Taez early Saturday, shortly after a UN humanitarian truce came into effect, witnesses said.

Two air raids targeted Shiite Huthi rebel positions in Arbaeen Street in Taez, where clashes between the Iran-backed insurgents and fighters loyal to exiled President Abedrabbo Mansour Hadi continued after the truce began at midnight, witnesses said.

Violence continued through the night in Taez, with witnesses saying the Huthis had also bombed several neighbourhoods.

Yemen's official news agency, which is run by the exiled government, accused the Huthis and allied troops loyal to former president Ali Abdullah Saleh of sending reinforcements to Taez ahead of the truce.

Besides the raids in Taez, no other airstrikes have been reported in the country since the ceasefire came into effect. Warplanes flew sorties over Sanaa, but there were no attacks after midnight, witnesses said.

The Saudi-led coalition has not committed to the truce, which a Saudi official described as "useless," questioning whether the rebels would stick to it.

The six-day pause to allow in desperately needed aid was declared after UN Secretary General Ban Ki Moon received assurances from Hadi and Huthi rebels that it would be respected.