Zeid Ra'ad al Hussein, the UN's Commissioner for Human Rights, told the UN Security Council that he had "observed with extreme concern" incidents of heavy shelling in areas with high concentrations of civilians.
While saying all parties were responsible for civilian suffering, he added that "a disproportionate amount appeared to be the result of air strikes carried out by coalition forces."
The comments are the latest in the international condemnation of the Saudi-led campaign, which has the backing of nine Middle Eastern and African states, along with political support from Britain and the US, with Washington offering logistical assistance to Riyadh.
It is estimated that more than 2,600 civilians have been killed since fighting broke out in March, with a UN report in September concluding that two-thirds of civilian deaths "had allegedly been caused by coalition airstrikes, which were also responsible for almost two-thirds of damaged or destroyed civilian public buildings."
On top of civilian deaths, the coalition has also been accused of committing war crimes in Yemen through the bombing of residential areas, while western allies such as Britain and the US have been accused of complicity and joint responsibility in the alleged crimes and civilian deaths.
NGO Human Rights Watch (HWR) accused the US of being complicit in 300 illegal civilian deaths in Yemen through its logistical support for operations, while there are calls for the UK and France to halt the sale of arms to Saudi Arabia.
Despite the pressure from the UN and non-government organizations, Saudi Arabia's western allies have so far refused to reign in their relationship with Riyadh, arguing that the operation in Yemen is key to defeating the Houthi rebel group and returning the internationally recognized government of President Abd Rabbuh Mansur Hadi to power.