Regional rivals Saudi Arabia and Iran traded accusations Tuesday over the escalating conflict in Yemen, which the UN rights chief warned was on the brink of "total collapse".
Aid groups warned of a humanitarian crisis unfolding with air and sea blockades making it impossible to send desperately needed assistance as casualties mount.
Explosions lit up the skies over the Yemeni capital on Monday night in the heaviest bombing raids yet of a six-day air war led by Riyadh against Shiite rebels.
The Huthi rebels and their ally, former president Ali Abdullah Saleh, "decided with the support of Iran to destabilise Yemen," Saudi Foreign Minister Prince Saud al-Faisal said.
"We are not warmongers, but when they beat the drums of war we are ready," Saud told the Shura Council advisory body.
Tehran hit back, accusing Riyadh of putting the entire Middle East in jeopardy.
"The fire of war in the region from any side... will drag the whole region to play with fire," Deputy Foreign Minister Hossein Amir-Abdollahian said.
Iranian state media rejected as "utter lies" claims Tehran had sent arms to Yemen, but said it had dispatched non-military aid, including food and medicine.
The war of words pitting Shiite Iran against its Sunni Arab neighbours came as marathon nuclear talks between Tehran and world powers entered a crucial phase in Switzerland.
The coalition has vowed to keep up the strikes until the Huthis end their uprising against President Abedrabbo Mansour Hadi, who has fled to Saudi Arabia.
But with little sign of an imminent halt to the conflict, the UN said it relocated its peace envoy for Yemen, Jamal Benomar, to Jordan at the weekend and pulled out its last 13 foreign employees from the country.
Benomar is working on reviving peace talks despite the air campaign, UN spokesman Farhan Haq told reporters, downplaying reports the envoy had lost support from Gulf governments.Huge blasts were heard overnight in Sanaa when coalition forces hit a missile depot belonging to the renegade Republican Guard, which is loyal to Saleh.
"The bombing was the heaviest I have ever heard in my life. The explosions lit up the skies of Sanaa," said 30-year-old resident Amr al-Amrani.
Early Tuesday, air strikes targeted two Huthi-held camps and Republican Guard soldiers in the southern town of Daleh.
Coalition warplanes also raided a Guard air base in the southwestern city of Taez, witnesses there said.
For the first time since the operation began, warplanes bombed renegade troops in the Shiite-populated city of Dhammar, a Huthi stronghold south of Sanaa.Deadly clashes have broken out between the rebels and tribes, militiamen and residents who oppose their power grab.
Doctors Without Borders (MSF) said it had received more than 550 patients in the southern city of Aden since March 19 as a result of fighting.
"We urgently need to find ways to get humanitarian relief and personnel inside the country," said MSF`s Greg Elder.
The UN said that since Friday, at least 93 civilians had been killed and 364 injured.
"The situation in Yemen is extremely alarming, with dozens of civilians killed over the past four days," UN High Commissioner for Human Rights Zeid Ra`ad Al Hussein said.
"The country seems to be on the verge of total collapse."
He denounced reported attacks by Huthi-linked fighters on three hospitals in Daleh that caused an unknown number of casualties.
A spokeswoman for European Union foreign policy chief Federica Mogherini said the conflict was having "terrible consequences" for civilians.
"We call on all parties to the conflict to ensure the protection of civilians, that civilian infrastructure is not directly targeted," the EU said.
The International Committee of the Red Cross said it was trying to negotiate the safe arrival of a plane stocked with medical supplies to treat up to 1,000 people.
"There are casualties across the country," said the ICRC`s Cedric Schweizer.
Amnesty International said at least six civilians, including four children, had burned to death in strikes on Tuesday morning in Ibb in central Yemen.
"It is becoming increasingly apparent that the Saudi Arabian-led coalition is turning a blind eye to civilian deaths and suffering caused by its military intervention," it said.
