"The recent report that two people became seriously ill in the United Kingdom of Great Britain and Northern Ireland as a result of exposure to a nerve agent is of serious concern," Ahmet Uzumcu, director-general of the Organisation for the Prohibition of Chemical Weapons (OPCW), said in a statement.
"It is extremely worrying that chemical agents are still being used to harm people. Those found responsible for this use must be held accountable for their actions."
Uzumcu said British Foreign Secretary Boris Johnson had called him on Monday evening to discuss the ongoing investigation into the attempted murder of Skripal and his daughter in the English city of Salisbury on March 4.
So far 192 member nations have joined the OPCW. In the past two decades, the body has overseen the destruction of some 94 percent of the world's declared chemical weapons stockpiles.