The British defense secretary Michael Fallon has seen government analysis indicating that UK-made cluster munitions were used by the Saudi-led coalition in the current conflict in Yemen.

It is understood the government's own investigations back up media reports that such cluster bombs have been deployed in the war, in which Britain is helping to train Saudi forces.

It is understood ministers have still not been given definitive confirmation one way or the other by Saudi Arabia, which has publicly denied the allegations and claimed that UK-made cluster bombs found are the relics of old conflicts.

Establishing the truth is important because the UK is a signatory to a 2010 international treaty banning the use of cluster munitions. The weapons leave mini-bomblets that can explode much later, killing civilians. The Cluster Munitions Convention commits the UK to disposing of all cluster munitions and working to prevent their use by anyone else. Saudi Arabia is not a signatory.

Reports from ITV, Sky News and Amnesty International have all pointed to bombs made in the UK and exported before the ban having been dropped in the ongoing war.

Philip Hammond, then the foreign secretary, pledged in May that the Ministry of Defense would investigate fully and seek concrete assurances from Saudi Arabia that there has been no use in the current conflict of British-made cluster munitions. At that time, ministers said the government does not possess any evidence that such weapons have been deployed, and suggested that the bomb found by Amnesty International could have been from a previous conflict in the region, adding that the last supply of this weapon to the Saudis was in 1989.

Earlier this month, No 10 delivered a rebuke to Boris Johnson, the foreign secretary, for critical remarks at a conference saying that Saudi Arabia was engaged in puppeteering and proxy wars in the Gulf. Downing Street said that was not the official government position. The UK is a firm ally of Saudi Arabia in the war in Yemen, with British military personnel helping train its troops to how to target bombs. Britain has also sold billions of pounds in defense equipment including planes to the Saudi military since the start of the war.