Four senior advisers of Islamic State (IS) have been killed following a US forces airstrike in Afghanistan's Kunar province, officials said on Sunday. "US Forces-Afghanistan has confirmed the death of four senior advisers of the IS in a strike that also killed Abu Sayid, a senior IS leader, in Kunar province on July 11 this year," Xinhua news agency cited a statement by US forces in Afghanistan as saying. The four eliminated IS elements were identified as Sheik Ziaullah, Mulawi Hubaib, Haji Shirullah and Assadullah, said the statement, adding that all of the four had played crucial role in Afghanistan. "We will be relentless in our campaign against IS, and there are no safe havens in Afghanistan," the statement quoted John Nicholson, commander of the US Forces-Afghanistan, as saying. Hundreds of IS militants including three top commanders have been killed during the Afghan and NATO forces operations over the past year.