
While chanting slogans, the protesters hoisted placards and waved flags of Khan's Pakistan Tehreek-e-Insaaf party.
Khan had earlier called for protests on Sunday.
"In a democratic system the final voice will be the voice of the people. And the voice is the people is Imran Khan," Ambareen Turk, a local party activist who joined Islamabad demonstrators, remarked.

Khan's government collapsed early Sunday following a 13-hour session marked by repeated delays and extended speeches from members of his Pakistan Tehreek-e-Insaf party.
The no-confidence resolution received 174 votes in the 342-member parliament, giving opposition parties the necessary majority to allow Monday's (April 11) vote to install a new premier.

Khan has enraged the US during his term, praising the Taliban takeover of Afghanistan last year and accusing the US of being behind the attempt to depose him more recently. The charge was dismissed by Washington.

In Karachi, one poster said, "No to imported government," while protesters screamed, "Any friend of America is a traitor" referring to former PM Na Qwaz Sharif and his party PML-N.
Quetta, Peshawar, Mardan, and other places organised smaller protests.

Shehbaz Sharif, an opposition leader, filed his nomination for Prime Minister of Pakistan to the legislature on Sunday, according to his party.
The younger brother of three-time Prime Minister Nawaz Sharif, Shehbaz Sharif, has led an opposition effort in parliament to depose former cricket star Khan, and he is largely projected to succeed him following a vote on Monday.