Saudi-led coalition warplanes launched fresh air strikes against Shia rebels across Yemen on Wednesday despite international concerns over the escalation after the suspension of peace talks.
The coalition resumed strikes days after UN-brokered peace talks in Kuwait between representatives of the government and the Iran-backed Houthi rebels ended without a breakthrough.
The coalition, which has been battling to prop up Yemen's government against the Houthis since March 2015, hit rebel positions across northern Yemen, said coalition officials and tribal sources.
That came a day after coalition jets struck targets around Yemen's rebel-held capital, Sanaa, for the first time in three months.
The United Nations said it was alarmed at the resumption of air raids.
"The secretary-general is deeply concerned about reports of increased fighting between various parties in Hajjah, Saada and Sanaa provinces including over the past few days," said Farhan Haq, deputy spokesman for UN chief Ban Ki-moon.
"The reported escalation in fighting exacerbates the already dire humanitarian and human rights situation and the suffering of the Yemeni people."
France said its Foreign Minister Jean-Marc Ayrault spoke by phone with his Saudi counterpart Adel al-Jubeir and emphasised the importance of a ceasefire to pave the way for a political solution in Yemen.
Iran, which Riyadh accuses of supporting the Houthis, denounced the international community's "inaction" while Saudi Arabia carried out what it called "atrocities" against Yemenis.
It called on the UN and countries that supply arms to Saudi Arabia to make "effective efforts to stop these attacks and... protect civilians."
The renewed violence came as the Pentagon said it had approved the possible sale to Saudi Arabia of up to 153 tanks, hundreds of machineguns and other military gear in a deal worth $1.15bn.
State Department spokeswoman Elizabeth Trudeau said she was "very concerned" by Tuesday's casualty reports, but did not directly comment when asked about worries that US weapons being sent to Saudi Arabia could be used against civilians.
Border clashes 
Saudi Arabia said it had intercepted missiles fired from Yemeni territory towards two of its southern towns on Wednesday morning.
The rebel-controlled Saba news agency said one missile was launched towards a military base across the frontier, without providing further details.
The coalition responded by targeting rocket launch positions belonging to Houthis in Amran province, north of Sanaa, it said in a statement.
Tribal sources said air strikes hit the rebels' positions across their northern stronghold province of Saada on Wednesday.
Clashes also flared between coalition forces and the insurgents close to the Saudi border, military sources told AFP.
Yemeni officials said government forces and Houthi rebels were engaged in fierce fighting in Haradh, which borders the southern Saudi province of Jazan.
The rebel-controlled Saba news agency said one missile was launched towards a military base across the frontier, without providing further details.
Coalition air raids on Sanaa on Tuesday hit a factory, killing 14 people, according to medics. Air strikes also temporarily closed Sanaa's international airport.
Coalition spokesman General Ahmed Assiri said renewed coalition strikes in Yemen were justified after the failure of negotiations and a series of rebel violations of a three-month truce.
Foreign Minister Abdulmalek al-Mikhlafi, head of the government's delegation to the Kuwait talks, accused the rebels of escalating the situation to make the negotiations fail.
At a news conference in Riyadh, he condemned the Houthis and forces loyal to their ally, former president Ali Abdallah Saleh, after they created a council to govern Yemen.
Mikhlafi said the body was "unconstitutional", and called on MPs to boycott a meeting to be held on Saturday to approve its creation.
The UN says more than 6,400 people, mostly civilians, have been killed in Yemen since the coalition air campaign began last March.
The fighting has also driven 2.8mn people from their homes and left more than 80% of the population needing humanitarian aid.