No more money from Welsh ministers should go to a company that makes weapons for Saudi Arabia, Plaid Cymru's Adam Price said.
The Welsh Government and US defence firm Raytheon invested £1m in a site in Deeside which maintains RAF spy planes.
Saudi Arabia's war in Yemen has claimed more than 10,000 lives. Mr Price claimed the firm's Welsh operations help supply missiles to the country.
First Minister Carwyn Jones said he would look into the matter.
Saudi Arabia's three year conflict with Yemen has claimed more than 10,000 lives. The United Nations has warned that 13m are facing starvation.
The Saudi government has also admitted that a team of agents murdered journalist Jamal Khashoggi, a prominent critic who was living in self-imposed exile in the US.
A US Department for Defence document, cited by Mr Price, said Raytheon was awarded work for the procurement of 618 "air-to-ground missiles", "containers, component parts/support equipment (spares) and engineering technical assistance for the government of Saudi Arabia".
It suggests that 15.6% of that work will be conducted in Glascoed, in Wales, and 6.2% in Glasgow.
The Welsh Government's investment is at Deeside, where the company maintains long-range RAF spy planes.
Mr Price said the document "confirms that Rayethon's Welsh operations are directly and substantially involved in delivering hundreds more air to ground missiles to the Saudi Arabian military".
"According to CNN Rayethon's weapons have been used in the targeted bombing of civilians in Yemen," the party leader said.
In the Senedd on Tuesday Mr Price asked Mr Jones to commit to not giving "a single penny more of public money from Wales... to a company involved in the supply of weapons of this murderous and barbaric regime".
Mr Jones replied that Mr Price had "raised an important issue there in terms of Rayethon".
"It is not clear what the involvement of the Rayethon plant on Deeside is with regard to Saudi Arabia," he said.
"I will however find out, and I will write to him once I establish what the connection is."
'Are ethics not devolved?'
Earlier Mr Price asked if Ms Jones was content that the Royal Air Force "are training Saudi Arabian pilots at RAF Valley on Ynys Mon teaching the techniques that can be used in the conflict in Yemen?"
Defence minister Mark Lancaster told Plaid Cymru MP Jonathan Edwards in October that 30 RSAF pilots have undertaken training at RAF Valley as part of their training programme in the last ten years.
"These are matters of course that are not devolved," Mr Jones responded.
"I certainly join with him in wishing to see a peaceful solution to the conflict in Yemen. The current situation is unsustainable, innocent lives are being lost," he said.
"Are ethics not devolved," Mr Price replied.