Washington: Expressing deep concern over reports about execution of over 100 people in Syria last week, the US has said that those responsible for serious violations of international humanitarian law must be held accountable.

"We are horrified by the reports that more than 100 people were executed on May 2, in al-Bayda, reportedly by regime forces, including the Shabiha," White House spokesman Josh Earnest told reporters while travelling with US President Barack Obama to Ohio.

"Those responsible for serious violations of international humanitarian law and serious violations and abuses of human rights law must be held accountable," Earnest said.

"As Bashar al-Assad (the Syrian President) continues to cling to power, we will not lose sight of the men, women and children who are being killed by his regime," he said in response to a question.

PTI