A US arms giant with a factory in Fife producing laser guided systems for smart bombs has been linked to another alleged war crime in Yemen.

A new report by Human Rights Watch says that an airstrike in September that killed at least 31 civilians, including three children, was unlawful.

The attack is the latest controversial bombing in Yemen’s war, adding to the dozens of war crime allegations made against Arab military forces backed and armed by the UK.

War-torn Yemen is also suffering a humanitarian catastrophe with millions of people facing starvation because the country is about to run out of food. Oxfam warned that Yemen is “slowly being starved to death”.

The UK has been supplying a Saudi-led coalition fighting Houthi rebels with Paveway IV missiles produced by US arms firm Raytheon at its factory in Glenrothes. Despite many allegations that hospitals and schools have been bombed by the coalition the UK Government has repeatedly refused to suspend arms sales to the Saudis.

The new report by HRW said coalition warplanes killed several dozen civilians in three apparently unlawful airstrikes in September and October 2016.

Just before dawn on September 10, coalition planes bombed a water drilling rig near Beit Saadan village in Arhab district, around 18 miles north of Sanaa. Multiple strikes that morning killed at least 31 civilians and wounded 42 others.

Yehia Abdullah, a 34-year-old teacher, lost his brother in the first strike on Ahrab. He said: “I saw five bodies including my brother Muhamad. First I found my brother’s severed leg outside the [workers’ shelter], about six meters, his arm on the door … and half his body buried in the ruins.”

War crimes investigators who visited the site found remnants of two US-made GBU-12 Paveway II laser guided 500-pound bombs. Human Rights Watch said part of the guidance system was produced by Raytheon in the US in October 2015, according to markings on a bomb fragment.

Earlier this year, we revealed that fragments of a bomb found at the scene of another alleged war crime in Yemen linked to Raytheon in Scotland. A code – 15090-2271709-3 MFR U07GO – engraved on the fragment revealed it was made by Raytheon and a sub-contractor called Border Precision, a firm based in Kelso before it closed down last summer.

HRW said: “The attacks underscore the urgent need for foreign governments to suspend all arms sales to Saudi Arabia and for the United Nations human rights office to send additional investigators to Yemen to carry out credible investigations of alleged abuses by the coalition, the Houthis and their allies, and all other parties to the conflict.”

Between March 2015 and October 2016, at least 4125 civilians were killed and 7207 wounded in Yemen, according to the UN Office of the High Commissioner for Human Rights (OHCHR) – the majority by coalition airstrikes. OHCHR reported in August that airstrikes had been the “single largest cause of casualties” over the past year.

The Houthis and their allies are also alleged to have committed war crimes. Human Rights Watch has documented the use of UK-made weapons in three apparently unlawful coalition attacks in Yemen.

Andrew Smith of Campaign Against Arms Trade said: “There is clear and overwhelming evidence that Raytheon has been complicit in, and profited from, war crimes. The destruction in Yemen has created a humanitarian catastrophe, but to Raytheon it’s just another business opportunity. Bombs made in Scotland are falling from the sky and could well be landing on civilian targets.”

Both Raytheon and the Saudi Arabia Embassy in London declined to comment.

If Boris Johnson believes that Saudi Arabia is a puppeteer state that twists Islam to fight proxy wars, then he must use his visit to call for an end to the bombing Andrew Smith, CAAT

Meanwhile, Oxfam warned that Yemen could run out of food this winter.

Mark Goldring, Oxfam GB Chief Executive, said: “Yemen is being slowly starved to death. First there were restrictions on imports – including much needed food – when this was partially eased the cranes in the ports were bombed, then the warehouses, then the roads and the bridges. This is not by accident – it is systematic.

“The country’s economy, its institutions, its ability to feed and care for its people are all on the brink of collapse. As one of the principle backers of this brutal war Britain needs to end its arms sales and military support to the Saudis and help put Yemen on the road to peace.”

CAAT was also critical of Foreign Secretary Boris Johnson who was in Saudi Arabia this weekend on an official visit. Prior to the trip, Johnson was slapped down by Downing Street after accusing Saudi Arabia of being a “puppeteer” and waging proxy wars in the Middle East.

Publicly humiliating her foreign secretary, Theresa May disowned his remarks with a spokeswoman for the prime minister saying he was setting out his own views but would be sticking to the government’s line while in Saudi Arabia.

CAAT said: “If Boris Johnson believes that Saudi Arabia is a puppeteer state that twists Islam to fight proxy wars, then he must use his visit to call for an end to the bombing and an end to the arms sales. The UK has armed and supported the Saudi-led bombardment, and the hell that it has unleashed on Yemen now it must do everything it can to stop it.”

In reply, a FCO spokeswoman said: “As the Foreign Secretary made very clear last weekend, we are allies with Saudi Arabia and support them in their efforts to secure their borders and protect their people. Any suggestion to the contrary is wrong and misinterpreting the facts.”