More than one-third of Saudi-led airstrikes in Yemen have hit civilian targets, the Guardian has reported.

The findings were revealed after a study was conducted by the Yemen Data Project – a group of anonymous academics, human rights organisers and activists.

Their research documented over 8,600 airstrikes in the region from March 2015, when the bombing campaign began, to the end of August this year and claims 3,158 of these hit non-military targets.

Roughly 3,500 strikes are reported to have struck military sites, with a further 1,800 strikes classed as unknown, where the classification of a strike could not be determined.

Saudi Arabia began bombing Yemen after Houthi rebels captured the country's capital Sana'a with the backing of Iran.

The findings of the study contradict the claim that Riyadh tried to minimise civilian casualties. However, Saudi Arabia has categorised the findings as "vastly exaggerated", reports the Guardian.

Despite that, the figures are expected to put renewed pressure on the Gulf state and its US and British backers for human rights violations.

They will also put increased scrutiny on UK arms sales to Saudi Arabia, which have eclipsed £3.3bn ($4.29bn) since the Yemen campaign began. It follows a joint report by the Business, Innovation and Skills committee and International Development committee which calls on the UK to cease arms sales to Saudi Arabia.

The report states: "It seems inevitable that any violations of international humanitarian and human rights law by the coalition have involved arms supplied from the UK.

"We therefore recommend that HM Government suspend sales of arms which could be used in Yemen to Saudi Arabia until the independent, UN-led investigation has come to its conclusions and then review the situation again."

The UN has so far put the death toll to more than 10,000 in Yemen, with just under 4,000 reported as civilians.

Although a ceasefire was agreed in April, fighting and airstrikes have continued.