Police in Pakistan's capital fired teargas on Friday as they clashed with supporters of jailed former prime minister Imran Khan who were holding an anti-government rally in defiance of a ban on congregating in the city.

Authorities had cordoned off Islamabad and blocked mobile phone services to prevent the assembly, as the city remained on high alert ahead of a series of high-level diplomatic events, including the SCO summit.

Pakistan authorities have sealed off Islamabad and suspended cellphone services to prevent protests by supporters of jailed former PM Khan.