RIYADH —British Prime Minister Theresa May said on Tuesday she would raise “hard issues” with Saudi Arabia’s leaders on a visit to the country, as critics urged her to pressure Riyadh over its air war in Yemen and human rights record.

May also said she was appalled by reports of a chemical weapons attack in northern Syria that killed dozens of people, including 11 children, and called for a prompt investigation.

She was expected to explore ways of boosting trade with the kingdom during the two-day visit, her second to a Gulf Arab state since Britain voted to leave the European Union.

Saudi Arabia is the country’s largest Middle East trading partner, with British exports worth $8 billion in 2015.

May, who has launched a drive to secure trade deals after launching divorce proceedings with the EU, said she would stand up for both human rights and Britain’s national interests in her talks in the world’s top oil exporter.

Saudi Arabia is a major customer for British defense companies and an ally in the fight against Islamist militancy.

Britain’s supply of aircraft and weapons has come under scrutiny because of the war in Yemen.

A Saudi-led coalition of Arab states has launched thousands of air strikes in an effort to dislodge Iranian-aligned Houthis from the capital Sanaa and restore President Abd-Rabbu Mansour Hadi to power.

The two-year-old civil war has killed more than 10,000 people, half of them civilians.