Pakistan's former prime minister Imran Khan could be arrested later on charges of threatening police officials and a judicial magistrate.
It comes after he hurled threats against Islamabad's police chief and a female judge for what he claimed was the arrest and alleged torture of a close aide who is facing sedition charges.
Mr Khan's nephew tweeted on Sunday: "Arrest attempt might take place between 4am to 6am.
"I request lawyers to call for country wide strike. Whole country will close. Leader Imran Khan is red line."
Earlier, the politician accused the government of temporarily blocking YouTube in the country to prevent people from listening live to a speech he gave at a political rally.
Pakistan's electronic media regulator announced a ban on the live airing of Mr Khan's speeches because of what it called his "hate speech" against state institutions.
"Mr Imran Khan… in his speeches/statements is continuously… levelling baseless allegations and spreading hate speech through his provocative statements against state institutions," the Pakistan Electronic Media Regulatory Authority (PEMRA) said in its statement on Saturday.
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PEMRA said it was, with immediate effect, banning news channels from broadcasting his speeches live, but said recorded speeches could be aired.
Mr Khan's speeches were "prejudicial to the maintenance of law and order and likely to disturb public peace and tranquility", PEMRA added.
Mr Khan – who has been pushing for new elections in Pakistan after being ousted from power in April – has been delivering fiery speeches at gatherings across the country.