A coalition of Arab states vowed to coordinate political and military efforts to restore order in Yemen as Saudi-led warplanes Monday launched new air strikes on Houthi Shiite rebels.
The raids killed at least 12 Houthi insurgents and allied forces as fighting continued across several provinces, military and local sources said.
Sheikh Mohammed bin Zayed al-Nahayan, the Abu Dhabi crown prince and armed forces chief of the United Arab Emirates (UAE), said the coalition is now working on military and political fronts to reestablish the legitimate authority in Sanaa.
The campaign's new phase is based on a "multilayered strategy, including military, as well as politics and development, to reestablish the legitimacy," he said on a visit to his troops in Saudi Arabia taking part in the coalition.
"We have no other choice but to succeed in the test of Yemen," Sheikh Mohammed said, quoted in UAE daily Al-Ittihad, ahead of another UN Security Council meeting Monday on efforts to halt the conflict.
He stressed the UAE's determination to act alongside other Arab countries to confront "regional agendas that reflect greed", an apparent reference to Gulf neighbour Iran which supports the rebels but denies having armed them.
On the other side of the Gulf, Iran's Revolutionary Guards chief said Saudi Arabia was verging on collapse as Tehran's position strengthened, comparing Riyadh to Israel because of its intervention in Yemen.
The remarks by General Mohammad Ali Jafari were a further sign of deteriorating relations between Tehran and Riyadh, after recent heavy criticism by Iran's supreme leader and other top officials.
"Today, treacherous Saudi Arabia is stepping in the footsteps of Israel and the Zionists," the official IRNA news agency quoted Jafari as saying.
"Today the Saudi dynasty is on the verge of decline and fall," he said, asserting that Iran was in the ascendancy.
The Saudi government said Monday the nine Arab countries that make the coalition want to help Yemen "reinstate security and stability, away from any hegemony or foreign meddling that aims to foment sedition and sectarianism."
Yemen is expected to be the focus of a meeting of Gulf foreign ministers on Thursday, ahead of a leaders' summit on May 5.
The latest air raids hit five schools converted by the Houthis into military bases in Ataq, the capital of the southern province of Abyan, military sources said.
The raids killed at least 12 insurgents and troops loyal to former president Ali Abdullah Saleh, who has allied himself with the northern rebels against the government of President Abedrabbo Mansour Hadi, the sources said.
Also in Abyan, warplanes targeted rebel positions on the outskirts of Loder, the province's second largest city, witnesses said.
Clashes were ongoing southwest of Loder between rebels and southern forces that have sided with Hadi, they added.
Fierce fighting also raged in the central city of Taez, with the warring parties using tanks and rocket-propelled grenades inside residential areas, officials said.
At least 16 civilians were killed in Taez on Sunday, before coalition warplanes reportedly hit rebel positions east of the city overnight.
The United Nations says more than 1,000 people have been killed in fighting in Yemen since late March, when Riyadh assembled the coalition in support of Hadi.
The embattled leader asked for Gulf intervention after the rebels closed in on his refuge in the southern port city of Aden after they had overrun several provinces since September, including the capital.
Hadi has since fled to Riyadh.
Air strikes have continued despite a coalition announcement last week of an end to its air campaign dubbed "Operation Decisive Storm".
Saudi Arabia says it has started deploying National Guard troops on its border with Yemen, joining members of the Saudi border guard and army who have reinforced the frontier since late March.