GENEVA — United Nations human rights officials expressed alarm on Friday at a sharp rise in civilian casualties in Yemen since peace talks collapsed last month, the great majority of them inflicted in airstrikes by a coalition led by Saudi Arabia.

At least 329 civilians have been killed, and at least 426 have been injured since the beginning of August. Fighting resumed after Aug. 6, when talks collapsed between the Saudi-led coalition supporting Yemen’s president, Abdu Rabbu Mansour Hadi, and forces aligned with Houthi rebels supported by Iran who control the capital and large portions of the country.

The toll was reported as Saudi Arabia and Arab allies waged a diplomatic campaign at the United Nations Human Rights Council to stave off an international investigation into the conduct of hostilities and possible war crimes.

Heavy Saudi pressure on Western governments and businesses succeeded in stalling a similar initiative in the Council last year; diplomats say the Saudi foreign minister, Adel al-Jubeir, has again lobbied against an independent international inquiry. They add that growing awareness of the bloodshed has made it harder for the United States and Britain, Saudi Arabia’s major suppliers of arms and munitions, to look away.