At least 81 civilians died and 109 were injured in Yemen during December as a ceasefire that began in the middle of the month quickly unraveled, the United Nations reported Tuesday.
The UN said that 62 of the civilian deaths in December were caused by airstrikes by the Saudi-led coalition that is fighting against Houthi rebels in the country.
The total civilian death toll between March, when the coalition began airstrikes, and the end of December stands at 2,975 with over 5,300 people injured.
The UN also warned that it had received reports of cluster bombs being used by coalition forces.
Meanwhile, two provincial governors loyal to Yemen's Saudi-backed President Abd Rabu Mansour Hadi survived a suicide attack on their convoy in Hadi's temporary capital, Aden, on Tuesday.
Aden Governor Aidarous Zubeidi's bodyguard died in the attack, which came less than a month after his predecessor was killed in a car bombing claimed by the Islamic State extremist group.
There was no immediate claim of responsibility for Tuesday's attack.
Local militias allied to Hadi and backed by Gulf forces recaptured Aden from the Iran-aligned Houthi Shiite rebels in July, but the government has struggled to impose its control.
Islamic State jihadists have claimed several deadly attacks in Aden. Al-Qaeda fighters, who control a large area of south-eastern Yemen, are also present in the city.
On Monday, Hadi inspected Aden's seaport, Yemen's main commercial port, after a newly formed official security force gained control of it from local militiamen who had been refusing to hand it over.
Elsewhere in Yemen, intense airstrikes have been reported in the last few days in an apparent stepping-up of the Saudi-led air campaign against the Houthis.
A school for blind children and adults in the capital Sana'a was hit overnight in one of the strikes, injuring four students, its director told dpa.
On Saturday, the Saudi-led coalition against the rebels announced the end of a ceasefire that had had little effect on the ground.
That move came on the same day that Saudi Arabia said it had executed prominent dissident Shiite cleric Nimr al-Nimr, sparking a furious response from Iran and from Shiites across the Gulf region and elsewhere.
Saudi Arabia fears that the Houthis will give Shiite Iran, its key regional rival, a strategic foothold in the Arabian Peninsula.
But its campaign against the rebels, launched in March, has made little progress since the recapture of Aden.
The rebels continue to claim regular attacks on Saudi border posts, and front lines in the centre of the country have barely changed in months.
The conflict is taking a massive toll on the civilian population of what was already one of the poorest countries in the Arab world.
More than 14 million Yemenis are at risk of food shortages and 21 million need some form of assistance or protection, according to figures published by the United Nations.