The Saudi-led coalition warned on Friday that all of Yemen's Saada province is a military target from 7 p.m., media reported.
The warning came hours after Saudi-led forces dropped leaflets, asking residents in Saada to leave before 7 p.m., Xinhua news agency reported citing Al Arabiya news.
The coalition of Arab and Gulf countries will target Houthis' locations in Saada, a northern region in Yemen, the report said, adding that all main roads in the province have been opened for civilians to leave until sunset.
Earlier on Friday, the coalition forces destroyed the headquarter of Houthi militants in Saada, a telecommunication complex and a mine factory.
The escalation came a day after US Secretary of State John Kerry backed here a Saudi plan to initiate a five-day truce in Yemen for sending humanitarian aid. He said if the Houthis agrees to the ceasefire, the truce could be renewed.
Meanwhile, the Houthis continued to attack the Saudi border city of Najran, where deaths and injuries were reported.
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Airstrikes by a Saudi-led coalition on Houthi rebels in Yemen have been going on since late March. More than 1,000 people have been killed and 3,000 injured in the airstrikes and in fierce fighting between the Shia Houthi group and tribal militia loyal to President Abd-Rabbu Mansour Hadi.
Riyadh and Washington have conditioned the proposed ceasefire deal on Houthi rebels agreeing to abide by its terms.