Saudi-led warplanes bombed targets in Yemen's Saada province, a bastion of Iranian-allied Houthi rebels, on Friday and Riyadh then announced a five-day humanitarian ceasefire to begin on May 12, conditioned on Houthis agreeing to the pause.
Hours before, Saudi authorities warned all civilians to leave the northwestern Saada region, which borders on Saudi Arabia, by sunset on Friday after threatening a harsh response to Houthi shelling of Saudi frontier towns earlier this week.
Saudi state television channel Al Ekhbariya said the whole of the arid, mountainous province would become a military target from Friday evening, hinting at an escalation in the Saudi-led coalition's six-week-old intervention in Yemen's civil war.
It aims to reverse the Shi'ite Muslim Houthi militia's cross-country advances -- seen by Saudi Arabia, the world's top oil exporter and arch-regional rival of Iran, as a security threat -- and restore President Abd-Rabbu Mansour Hadi in power.
Later on Friday, Saudi Foreign Minister Adel al-Jubeir proclaimed a five-day humanitarian truce to start on Tuesday at 11 p.m. Yemen time, and "subject to renewal if it works out" -- if Houthi forces agree to the pause.
"We hope the Houthis will come to their senses and realize the interests of Yemen and the Yemeni people should be the top priority for everyone," Jubeir told a news conference with US Secretary of State John Kerry in Paris.
"The requirements are first and foremost that there is a commitment by the Houthis and their allies ... to abide by this ceasefire," he added. "This ceasefire will (apply) throughout Yemen, or nowhere in Yemen."
International concern about the humanitarian situation has grown as the air strikes have killed more than 1,300 people, sent others fleeing from their homes and wrecked infrastructure, causing shortages of food, medicine and fuel.
"It is critically important that all countries are able to send as much relief, as efficiently, as quickly to as many Yemenis as possible," Jubeir added.
LASTING POLITICAL SETTLEMENT NEEDED, KERRY SAYS
Kerry said such a ceasefire would open the door to the possibility of peace talks. He cautioned, though, that a truce "is not peace" and said it was important that Yemeni leaders tried to reach a lasting political settlement.
"They are going to have to make tough choices more than just a ceasefire because even the most durable of ceasefire is not a substitute for peace," he said.
Riyadh had on Thursday proposed a five-day ceasefire to help civilians trapped in the conflict, if the Houthis themselves stopped fighting. But hours later, the Saudis warned of harsh retaliation against the Houthis after the rebels shelled some populated areas across the frontier.
Houthi mortar and rocket salvoes from Saada crashed into the Saudi city of Najran near the border on Tuesday and Wednesday, killing eight people, and Houthi forces shelled a Saudi air defense site near Najran on Thursday.
Two more Saudis were killed when Houthi shells struck a village in Jizan province, which also borders on north Yemen.
The official Saudi news agency SPA said the air raids, which started late on Thursday, hit four Houthi command-and-control centers, two in the Saada provincial town of Bani Maaz, and destroyed a mine factory in the ancient quarter of Saada city as well as a communications hub in the Mothalath area.
"Our work now is reaching those (Houthis) who planned these attacks and who are hiding in Saada, and the places where the militias are," Saudi-led coalition spokesman Brigadier General Ahmed Asseri told Al Ekhbariya state television.
Al Ekhbariya said all civilians in Saada province had been asked to clear out by 7 p.m. local time on Friday, when the entire rugged desert region would be designated a military zone.
"Saudi-led forces announce that all the main roads of Saada are available for civilians to leave until sunset," it said.
Saada residents said the air strikes damaged the tomb of the founder of the Houthi movement, Hussein al-Houthi.
There was also heavy shelling in the west of Saada province, near the Saudi-Yemen border, and 13 villagers were killed in strikes on Hajja province, also near the frontier, locals said.
The figures could not be independently verified.
In the southeastern province of Shabwa, coalition forces carried out at least five air strikes in the vicinity of Ataq airport and in Ataq city itself, local security sources said.