Yemenis are riding on the roof or hanging out the sides of taxi vans as severe fuel shortages in the capital Sanaa and other Houthi-held areas raise demand for public transportation, with people queuing for days to fill the tanks of their cars.

University students Amjad al-Amari and Ahmed al-Mutahar complain the fuel crunch is further disrupting their education in the war-torn Arabian peninsula country.

"When we arrive for lectures, we arrive late. We miss half and the professor considers us absent," said al-Amari. "We can't even find (taxis) and (the ones we get) are overcrowded."

People also struggle to reach markets and health centres. Twenty litres of petrol at fuel stations costs 9,500 rials ($16) and more than four times that on the parallel market.

Few people can afford this. Around 80% of Yemen's population needs assistance because of economic collapse in the seven-year war and a sea and air blockade by a Saudi-led coalition on areas held by the Houthis.

"The (fuel) crisis affects the whole population, from the ordinary to those on top. Neither officials nor dignitaries are excluded," civil servant Fawaz al-Sayaghi told Reuters.

Air and sea access to Yemen is controlled by the coalition that intervened in Yemen in early 2015 after the Iran-aligned Houthis ousted the government from Sanaa.

The alliance says the restrictions are needed to prevent arms smuggling, and accuses the Houthis of using ports for military purposes, charges the group denies.

Houthi officials said no fuel vessels have been allowed to berth at the country's main Hodeidah port since Jan. 3.

"We call on the concerned authorities, international organisations and the United Nations to lift the siege on oil derivatives and basic food commodities for people to have a minimum livelihood," said Muhsen al-Shahary, another civil servant in Sanaa.

Reuters