A fuel shortage is blighting life in the swathes of Yemen controlled by Houthi rebels, cutting electricity supplies, halting water pumps and stranding people in need of medical care as warring sides trade blame.

Energy scarcity is nothing new in a country ravaged by years of conflict, but queues at the pumps have been getting longer by the day since mid-June.

"What's happening is an injustice," said Sanaa resident Hames Al-Tawil as he waited in a snaking line of vehicles that reached the gates of the presidential palace four kilometres (2.5 miles) away.

Cars and vans parked three abreast stretched through the summer heat as far as the eye could see.

"At least have mercy on the people who've been waiting in this queue for three days," Tawil said through the rusted door frame of his pickup truck.

Yemen is already at breaking point, facing what the United Nations calls the world's worst humanitarian crisis after almost six years of violence.

The war, which has claimed tens of thousands of lives, pits the government against the Iran-allied Houthis, who in 2014 seized the capital Sanaa and much of the country's north.

The government and the Saudi-led military coalition backing it have accused the rebels of causing fuel shortages to boost their case for the lifting of crippling restrictions imposed by the coalition's naval and air blockade.

The Houthis meanwhile accuse coalition forces of obstructing fuel shipments to hamstring them economically.

A similar fuel crisis last year prompted aid group Oxfam to accuse warring parties in Yemen of "using the economy as a weapon of war".

Oxfam's Yemen director Muhsin Siddiquey warned last month of dire knock-on consequences if the fuel crisis persists.

Many Yemenis rely on groundwater extracted with pumps, while millions displaced by fighting and living in camps survive on water brought in by diesel-powered trucks.

"A protracted fuel shortage could put millions at risk of both contracting coronavirus and water-borne diseases like cholera because fuel is essential for the supply of clean water in Yemen," Siddiquey said.

Shortages have also affected hospital operations, halted transport services and sent prices of essential goods soaring.

One litre of petrol now sells for 1,200 riyals (two dollars) on the black market -- triple the price before the current shortages.

The Houthi-controlled Yemen Petroleum Company last month warned that its gasoline and diesel stockpiles were being depleted.

It charged that the coalition had for more than 90 days been preventing 15 tankers delivering 420,000 tonnes of petrol and diesel to the southwestern port of Hodeida.

The coalition has been inspecting ships bound for Hodeida, Yemen's main import hub, to block arms deliveries to the Houthis.

"We're hoping that a resolution is found very quickly because the impact on the population is devastating," the UN humanitarian coordinator in Yemen Lise Grande told AFP.

"Fuel that's needed to keep hospitals functioning and water plants functioning and irrigation systems functioning... is being held up in ships."

She said the country's economic situation "looks scarily similar to what we saw when the country was on the brink of famine 18 months ago".

The Houthis have also barred fuel convoys from government-held areas entering their territory, claiming the products are of substandard quality and don't meet safety guidelines, according to independent Yemeni energy sector sources.

The director of the Al-Thawra public hospital in Sanaa said shortages had had a "direct effect" on the facility, which no longer has a regular power supply.

"Due to the lack of fuel, the doctors and nurses cannot easily get to the hospital for their shifts," said Abdallatif Abu Taleb, adding that dialysis treatment and intensive care operations were particularly vulnerable.

In Hodeida, health centre worker Fatima said she had been queueing at the pumps for two days in temperatures of 40 degrees Celsius (104 Fahrenheit) to fill up.

"I left my car in the queue overnight," she told AFP, adding that food prices have surged due to higher transportation costs.

Bus driver Hani Mohammed, who plies the route between Hodeida and the capital Sanaa, suspended his service for a fortnight before resuming.

But the fuel shortage has forced him to double his fares.