Afghan Voice Agency (AVA): The sources told Al Jazeera that their conclusion was based on several factors, including the landing of two US C-17 Globemaster heavy transport aircraft at Nur Khan Air Base in Rawalpindi, near the Pakistani capital Islamabad.
They added that roads leading from the airport to the Red Zone in Islamabad have also been temporarily closed, indicating heightened security measures.
Finally, the sources said that both the Serena Hotel and the Marriott Hotel in Islamabad are evacuating guests and will not be accepting guests until Friday.
The Serena Hotel was the venue for the first round of talks between Iran and the US.