Top United Nations aid officer Stephen O'Brien said Tuesday that none of the warring parties in Yemen had respected a humanitarian ceasefire announced by the Saudi-led coalition, accusing both sides of failing to respect international law.

The Saudi-led coalition had announced a five-day truce beginning this past Sunday to allow in desperately needed aid including food, fuel and medicine. The coalition has been bombing Iran-backed Houthi rebels in Yemen for the last four months

"A humanitarian pause announced over the weekend has not been respected by any party to the conflict with air strikes and ground fighting reported in eight governorates," O'Brien told the 15-member UN Security Council Tuesday.

"Parties to the conflict continue to fail to meet their responsibilities under international humanitarian and international human rights laws," O'Brien said. "We continue to witness the death and injury of civilians."

On Tuesday, Saudi-led airstrikes hit the Houthi rebels who currently control Yemen's largest air base near the port city of Aden.

According to Yemeni health officials, more than 4,000 people have been killed and nearly 20,000 injured thus far in the four month conflict. O'Brien said that the UN could potentially help three million people in Yemen if the fighting would stop.

The aid plan "is live and ready to go now if only we could get a pause to stick," said O'Brien, who plans to visit Aden in the coming weeks.

Yemen was plunged into chaos last year when the Shiite Houthis seized control of the capital Sanaa and forced internationally recognized President Abed Rabbo Mansour Hadi to flee to Saudi Arabia.

A near total blockade of Yemen by Saudi Arabia has slowed shipments to the country and the Arab coalition inspects incoming ships to prevent any potential arms deliveries to the Houthis.

The Saudi-led coalition has been accused of killing civilians in its airstrikes against the Houthi rebels, but the country's ambassador to the UN, Abdallah Al-Mouallimi, has sought to downplay such concerns.

"I can assure you that no deliberate targeting of civilian sites is being undertaken by coalition forces," he told reporters.

bw/lw (AP, Reuters, AFP)