Saudi-backed Yemeni forces arrived by sea at the Red Sea port of Maydee near the border with Saudi Arabia late on Wednesday, residents said, opening up a new front in a nine-month-old civil war.
Northern Yemen is a stronghold of the Iranian-allied Houthi group, which has seized large parts of Yemen including the capital from forces loyal to the embattled Saudi-backed President, Abd-Rabbu Mansour Hadi.
Hadi's forces attempted to push from Maydee's port, pounded for weeks by air strikes and naval shelling, into the surrounding city, but ran into heavy Houthi resistance and landmines, residents told Reuters by telephone.
Major General Adel Qumairi of the pro-government forces told Saudi-owned Arabiya TV that his forces had "completely taken control" of the city.
But Yemen's state news agency Saba, run by the Houthis, quoted Sharaf Luqman, a spokesman for forces allied to the group, as saying the advance had been met by "heroic resistance" that caused them "great material and human losses."
Residents of Sanaa reported over 30 Saudi-led air strikes overnight on Houthi targets, in one of the capital's fiercest aerial bombardments of the war.
The strikes pounded the presidential palace and a mountain military base to the south of the city, causing children and teachers in several schools to flee for their lives.
"My classmate and I were at recess when a huge explosion hit the neighbourhood. We ran to the side and she fell to the ground in fear," Maha, a tenth grader in a Sanaa school, told Reuters.
"Everybody was screaming and the administration got us together and called our parents to take us out - all the students were in a panic."
There were no immediate reports of casualties.
A coalition of Arab states allied with the government of Yemeni President Hadi have been bombing Houthi insurgency since March last year, in addition to running training programmes and dropping weapons for Yemeni fighters loyal to Hadi.
The Saudi spokesman for the coalition, Brigadier General Ahmed Asseri, told Al Arabiya that a Houthi ballistic missile aimed at the kingdom overnight had exploded on launch.
Saudi Arabia on Saturday announced the end of a truce that had reduced fighting, but had been repeatedly violated by both sides.
The UN has declared the situation in Yemen to be a level-three humanitarian emergency, the highest on its scale, after about 80 percent of the country’s population fell into dire need of humanitarian aid.
Twenty million people in the country are in need of aid, 13 million are facing food shortages and 9.4 million are having difficulties accessing drinking water.
According to the United Nations, at least 6,000 people have been killed in the ongoing civil war in Yemen, nearly half of them civilians, and more than 27,000 injured since the war began.