The World Heath Organisation says just over a month of fighting in Yemen has left nearly 1,250 people dead, in a conflict affecting 7.5 million people.

The UN health agency described a "deteriorating" humanitarian situation, especially in Taez in the centre of the country where there have been heavy clashes.

Fighting and airstrikes by a Saudi-led coalition killed 1,244 people and injured 5,044 between March 19 and April 27, according to the latest WHO toll.

WHO receives its statistics from health facilities in Yemen, but since many people are unable to get to hospitals for treatment the real numbers are probably higher.

The latest toll was published as Saudi-led air strikes entered a sixth week on Friday, and did not include the 47 people killed in the latest strikes and clashes on the ground in Yemen's second city Aden.

The air strikes began in late March when the Iran-backed Houthi rebels and their allies advanced on the main southern city of Aden, where president Abedrabbo Mansour Hadi fled after the rebels seized large parts of the country, including Sanaa.

Mr Hadi escaped to Riyadh, which launched its campaign fearing an Iran-friendly regime taking control of its southern neighbour.

Supporters of the Shiite Houthi movement protest in Sanaa against the Saudi-led military air campaign which targets the rebels and their allies. ( AFP: Mohammed Huwais )

In Taez, 19 people were killed and 91 injured on April 26 alone, when the local Al-Thawra hospital was hit, WHO said.

The UN agency has also warned that most roads connecting Sanaa to the governorates of Aden, Taez, Al-Dhaale, and Lahj were "becoming gradually inaccessible, making the delivery of life-saving medicines a serious challenge".

Severe shortages of medicine and health staff were also being reported in areas where the violence was raging, and shortages of safe water were becoming acute across much of the country, it said.

WHO said disrupted electricity supplies and fuel shortages were being felt across Yemen and were hampering efforts to deliver medical supplies and keep health facilities and ambulances running.

The fuel shortages have also forced the World Food Program to halt its food distribution in Yemen where most of the stocks are in the hands of rebels.

People seem to be having difficulty accessing health facilities across Yemen, WHO said, and warned of rising numbers of cases of acute respiratory infections, acute diarrhoeal diseases, and malaria.

It also said it had received 44 alerts of suspected disease outbreaks, including measles dengue fever and meningitis.

The International Organisation for Migration meanwhile said that more than 12,000 people, both Yemenis and foreign nationals, had fled the country for the Horn of Africa since mid-March, mainly by boat.

More than 8,900 of them had fled into Djibouti and some 3,400 had made it to Somalia.

Russia attacks UN Security Council on failure to back ceasefire

The UN Security Council was unable to agree on a Russian-drafted statement demanding an immediate ceasefire or at least humanitarian pauses in the fighting in Yemen.

Russian ambassador Vitaly Churkin criticised the 15-member council, saying fellow envoys showed "amazing indecision" in the face of the worsening humanitarian crisis in Yemen.

"If you cannot agree to a motherhood-and-apple-pie statement, what can you agree on? I don't understand," Mr Churkin told reporters following the behind-closed-door meeting.

Russian ambassador to the UN Vitaly Churkin has urged the Security Council to back a Russian-drafted immediate ceasefire in Yemen. ( AFP/Getty: Spencer Platt )

Russia had requested the urgent meeting after UN secretary-general Ban Ki-moon warned that fuel shortages were threatening to bring all relief operations to a halt "within days".

Diplomats said the Russian statement appealing for action was not rejected out of hand but that the delegations needed time to consider the wording.

"There was a strong degree of council agreement on the desperate humanitarian situation in Yemen and need to return to political talks, but no agreement in the room on the exact working of the statement," a diplomat said.

Russia's diplomacy has been greeted with some suspicion given the country's close ties to Iran, which is supporting the Houthi rebels who have seized the capital Sanaa and forced Yemen's president into exile.

A US diplomat said Washington supports humanitarian pauses and was urging Saudi Arabia to take measures to ensure aid deliveries reach civilians trapped in the fighting.

"But let's be clear - it is the ongoing, unilateral actions of Houthis and forces loyal to former president (Ali Abdullah) Saleh that are responsible for the humanitarian crisis," he added.

AFP