Thirteen international news organizations, including the BBC, The Associated Press and The New York Times, have written a letter to the armed opposition in Syria asking for assurances that their reporters will not be abducted.

Over the past year, the letter says, the organizations have “witnessed a disturbing rise in the kidnapping of journalists while on assignment within the northern provinces of Aleppo, Idlib and al-Raqqa,” and elsewhere in Syria. The organizations estimate that more than 30 journalists are now being held, the letter said, and that as a result many of them have “decided to limit their coverage of the war.”

“We understand that, as in any war zone, reporters face great risk of injury and death,” the letter says, “and we accept those risks, but the risk of kidnapping is unacceptable, and the leadership is in a position to reduce and eliminate risk.”

Other news organizations signing the letter are The Washington Post, The Wall Street Journal, The Los Angeles Times, Reuters, Agence France-Presse, Atlantic Media, The Economist, The Guardian, The Telegraph and Getty Images.