WASHINGTON - Communications between Islamic State leaders in Raqqa, Syria, and persons in the Sinai Peninsula included boasts about the downing of a Russian passenger jet over the area, NBC reported on Friday, citing unidentified US officials. 'They were clearly celebrating,' NBC Nightly News quoted a US official as saying. The 'chatter' included a boast of taking down the plane on Saturday and how it was done. The US intelligence community intercepted a message from a Sinai group affiliated with Islamic State that warned of 'something big in the area' before jet crash.