The sister of a British journalist being held hostage by Islamic State militants has urged the group to re-establish contact with his family.

Jessica Cantlie said in a statement released Monday that the family had previously been in contact with the journalist's captors, but that the channel of communication had been lost. She said: "We implore I.S. to reinitiate direct contact."

John Cantlie, who has worked for a variety of British publications, was captured in Syria in late 2012. He has appeared in several propaganda videos released by the Islamic State group.

In recent weeks the militants have released online videos showing the beheading of U.S. reporter James Foley, American-Israeli journalist Steven Sotloff and British aid workers David Haines and Alan Henning.

It has threatened another American, Abdul-Rahman Kassig.