UNITED NATIONS (Reuters) - Top United Nations officials on Friday warned violence in Yemen was worsening and greater access was needed to the Houthi rebel-held north, particularly through the key Red Sea port of Hodeidah.

FILE PHOTO: A Houthi militant walks in front of a government compound, destroyed by recent Saudi-led air strikes, in Yemen's northwestern city of Amran July 27, 2015. REUTERS/Khaled Abdullah

U.N. aid chief Stephen O’Brien slammed Yemen’s government and a Saudi-led military coalition for “unilaterally denying or excessively delaying entry to vessels carrying essential cargo” to the port.

“It is simply wrong to insist these cargoes go to Aden, not Hodeidah,” O’Brien told the U.N. Security Council, appealing for countries to back a U.N. mechanism that started inspecting commercial shipments to rebel-held ports in May last year.

The United Nations has worked to avert attacks on Hodeidah port, where around 80 percent of Yemen’s food imports arrive.

The Saudi-led coalition, which has destroyed several cranes at Hodeidah port in air strikes, has accused the Houthis, the rebels fighting the Saudi-backed government in Yemen, of using the port to smuggle weapons and ammunition. The Houthi movement denies the allegations.

The coalition began an air campaign in March 2015 to help the Yemen government defeat the Iran-allied Houthis. O’Brien said monthly air strikes in 2017 had tripled from last year, while monthly reports of armed clashes were up 50 percent.

“The longer the conflict goes on, the higher the risk that terrorist groups will spread and the stronger their influence will become,” U.N. Yemen mediator Ismail Ould Cheikh Ahmed warned the Security Council.

Al Qaeda has exploited the conflict to try to deepen its influence in Yemen, repeatedly launching bomb and gun attacks. The United States regards al Qaeda in Yemen as one of the deadliest branches of the militant network.

O’Brien and Ould Cheikh Ahmed also pushed the Saudi-led coalition to allow civilian traffic to land at the airport in Yemen’s capital Sanaa.

“Most of the need is in the north of Yemen, not the south. Fact. Sanaa and Hodeidah best serve the north, not Aden. Fact.”Yemen’s catastrophe is completely manmade,” O’Brien said.

More than half a million Yemenis have been infected with cholera and some seven million are on the brink of famine, the United Nations has said.

Ould Cheikh Ahmed told the Security Council on Friday he is working to get a deal to secure the flow of aid, payment of salaries to civil servants and prevention of arms smuggling.

“It includes a practical plan to hand over the port to a committee of respected Yemeni security and economic figures, working under U.N. oversight and guidance,” he said.

He said Egypt, Iran, Oman, Saudi Arabia, the United Arab Emirates, the Gulf Cooperation Council and the Arab League all supported his proposals and that he was hoping to meet with the Houthis outside of Yemen to discuss the possible deal.