Pakistani police detained hundreds of supporters of ousted prime minister Imran Khan overnight ahead of a major sit-in planned by the former leader, senior party members and police sources said Tuesday, as the government pledged to block the protest.

Khan, a cricket star turned populist politician, was kicked out of power last month in a vote of no-confidence, but has since pressured the country's fragile new coalition government by staging mass rallies across the country.

Alleging that he was removed through a "foreign conspiracy", Khan plans on Wednesday to lead tens of thousands of supporters from his power base in the northwestern city of Peshawar to the capital Islamabad demanding fresh elections.

"Tomorrow I will be leading the largest march of Pakistan's history. I don't consider it politics but jihad," Khan said, referring to a term used by Muslims to describe a struggle.

Security was being built up across the country, with shipping container roadblocks hauled into place in Islamabad and the government quarter put on lockdown, while many entry and exit points around the city of Lahore -- around 380 kilometres (236 miles) away -- were also blocked.

"This (protest) is being done to divide the nation and promote chaos," Interior Minister Rana Sanaullah told reporters. "Nobody should be allowed to besiege the capital and dictate his terms."

"This march cannot be allowed to take place," Information Minister Marriyum Aurangzeb added.

Two police officials told AFP that more than 200 supporters of Khan's Pakistan Tehreek-e-Insaf (PTI) party were arrested in overnight raids in the nation's most populous province Punjab.

They were booked on public order offences and remain in detention, one of the sources said.

Activists of the Pakistan Tehreek-e-Insaf (PTI) party of ousted prime minister Imran Khan chant slogans during a protest
Activists of the Pakistan Tehreek-e-Insaf (PTI) party of ousted prime minister Imran Khan chant slogans during a protest AFP / Arif ALI

Fawad Chaudhry, the former information minister in Khan's government, accused police of not having the necessary warrants and put the number of arrested at more than 400.

"More than 1,100 houses were raided overnight. Police entered the houses without any warrants and insulted women and children," he tweeted.

One police officer was shot dead during a raid on a PTI supporter's house in Lahore, Punjab Chief Minister Hamza Shahbaz Sharif said.

Police have not officially commented on the arrests or allegations.

Attaullah Tarar -- a senior leader in new Prime Minister Shehbaz Sharif's PML-N party -- said at a press conference that protestors had been planning to join the march "with weapons".

"We have information that they have started collecting ammunition at various places," he told reporters.

Political analyst Hassan Askari Rizvi told AFP that Pakistan's all-powerful military was currently remaining neutral in the standoff but "they may try to defuse the situation if it gets worse".

On Saturday, senior PTI leader and former minister Shireen Mazari was arrested near her house in the capital over a decades-old land dispute. She was briefly detained before a court ordered her release.

In 2018, Khan was voted in by an electorate weary of the dynastic politics of the country's two major parties, with the popular former sports star promising to sweep away decades of entrenched corruption and cronyism.

He was brought down in part by his failure to rectify the country's dire economic situation, including its crippling debt, shrinking foreign currency reserves and soaring inflation.

Sharif is now grappling with the same crisis, as well as rising militancy and soured relations with the West.