Internet and social media services across Pakistan were severely disrupted Sunday night as the party of jailed former prime minister Imran Khan prepared to launch a massive online campaign ahead of elections next month.

Khan and most senior leaders of his Pakistan Tehreek-e-Insaf party (PTI) have been rejected as candidates for the February 8 vote in what they say is a campaign by the military-led establishment to thwart their participation.

PTI planned a massive national and global telethon Sunday evening to launch its manifesto and raise campaign funds, but internet disruptions started from early evening.

"The incident is consistent with previous social media filtering events which have all been imposed during opposition party rallies or speeches by opposition leader Imran Khan," said Netblocks, a watchdog organization that monitors cybersecurity and internet governance.

Netblocks Director Alp Toker told AFP the disruptions were affecting network providers across the country.

"Such nation-scale social media targeting political activities is almost unprecedented at this scale -- Venezuela is one other country that has used similar measures to limit opposition speeches and rallies," he said.

The Human Rights Council of Pakistan condemned the disruption as "a violation of international law".

"In the context of elections, all political parties should get the basic right of freedom of expression. It is the responsibility of the government of Pakistan to uphold the fundamental rights," it said on X.

- Defiant campaign -

Khan, 71, was ousted last year after falling out with Pakistan's powerful military leaders who backed him into power in 2018.

In opposition, he waged an unprecedented campaign of defiance against the military establishment which has directly ruled the nation for much of its history.

Khan accused them of engineering his removal from office in a no-confidence vote via a US-backed conspiracy, and of plotting an assassination attempt that saw him wounded.

After Khan's brief detention in May sparked unrest, PTI has been the subject of a widespread crackdown, with leading figures either jailed or forced to leave the party.

The election season has been somewhat muted, with most activity taking place in various courts where hundreds of cases are pending to determine who can take part.

The Supreme Court is due this week to rule on the lifetime disqualification of three-time prime minister Nawaz Sharif, who returned from exile earlier this year to launch a political comeback and could be a likely winner if he is allowed to run.