Prime Minister Theresa May has admitted that the UK Government does not know if civilians in Yemen have been killed by missiles partially manufactured in Scotland.

The weapons were later sold on by the Ministry of Defence to Saudi Arabia.

The Conservative Government has been fiercely criticised for selling arms for potential use in Yemen's civil war which pits the country's government, backed by Saudi Arabia, against Shiite Yemeni rebels.

Ministers have faced repeated calls to ban the sale of the arms.

Angus Robertson, the SNP's Westminster leader, asked Mrs May if she could say that no innocent civilians had been killed by the missiles.

Mrs May refused to be drawn saying that she would not comment before the results of official investigations.

Aides later confirmed that the government has pressed Saudi Arabia to properly probe all claims.

Mr Robertson said that thousands of innocent civilians had been been killed by Saudi air strikes in Yemen.

"It's beyond doubt that Saudi air forces bombing Yemen, flying planes that are made in Britain, by pilots that are trained by Britain, and they are dropping missiles that are made in Britain," he said.

He asked Mrs May: "Can you give this House an assurance that civilians have not been killed by Paveway IV bombs being dropped on Yemen which are partially manufactured in Scotland under licence by the Government, and if you don't know the answer to that question how can you possibly in good conscience continue selling them to Saudi Arabia?"

Mrs May told him that that UK ministers had urged the Saudi government to conduct thorough investigations into any incidents "before we reach a decision or a conclusion".

Campaigners have said that they fear that the Fife-made bombs are being used against civilians.

Raytheon, in Glenrothes, produces laser-guided systems for Paveway IV "smart bombs".

The MoD have admitted that they supplied Saudi Arabia with the bombs, originally earmarked for the RAF.