The coalition resumed strikes days after UN-brokered peace talks in Kuwait between representatives of the government and the Iran-backed Huthi rebels ended without a breakthrough.
The coalition, which has been battling to prop up Yemen's government against the Huthis 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 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.
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"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.
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 USD 1.15 billion.
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.