ISLAMABAD: Former Pakistan prime minister Imran Khan's three-year sentence for graft prompted scattered rallies around the country, but there was no sign of any mass uprising Sunday despite his call for supporters to protest.

His imprisonment has raised fresh concerns of violence ahead of an election due later this year -- that he is now disqualified from contesting -- and has cast doubt on the fairness of any vote that excludes him.

His lawyers complained Sunday they were being denied access to him for consultations so they can mount urgent legal challenges against his conviction.

They also raised concern for his confinement at Attock Jail, established 100 years ago on the outskirts of historical Attock city, around 60 kilometres (40 miles) west of the capital, Islamabad.

"He is a 70-year-old man and a former elected prime minister so legally he should be given a better class (of conditions) inside the jail," said Gohar Khan, a member of his legal team.

Officials from his Pakistan Tehreek-e-Insaf (PTI) party said around 50 supporters had been detained overnight as police moved swiftly against protests after Khan was arrested and whisked to jail.

At a court hearing Khan did not attend Saturday, a judge found him guilty of graft in relation to gifts he received while prime minister and sentenced him to three years in jail.

Anyone convicted of a criminal offence is disqualified from contesting elections in Pakistan, and Prime Minister Shehbaz Sharif said Sunday that parliament would likely be dissolved on Wednesday -- days ahead of the end of its natural term.

"I will dissolve my government and the National Assembly on August 9. The rest is in the hands of Allah the almighty," he told a rally in Punjab province.

"After that an interim government will take over and elections will be held."

This would give the incoming interim government until mid-November to hold an election, but there is already speculation it could be delayed following the release Saturday of the country's latest census data.

Law minister Azam Nazeer Tarar told a local television channel that constituencies would have to be redrawn according to the new census, warning there could be a delay to polls of up to two and a half months.

Khan's arrest and detention for three days in connection with the same case in May sparked deadly violence when his supporters took to the streets in the tens of thousands, clashing with police.

In the aftermath of his release, PTI has been targeted by a crackdown with thousands of arrests, reports of intimidation and muzzling of the press.

Khan was prime minister until April last year, when he was ousted in a vote of no-confidence he says was engineered by the country's powerful military.

Soon after police picked him up from his home in Lahore Saturday, a pre-recorded video was released on Khan's social media accounts calling for his supporters to protest in force.

"I have just one request and appeal, that you are not to sit silently at home," he said.

"This is a war for justice, for your rights, for your freedom... chains don't just fall off, they have to be broken. You must continue peaceful protest until you get your rights."

But party officials said Sunday there were no plans for a nationwide call to protest.

"As far as protests go, there's not a planned one as yesterday protesters were raided by the police and detained," an official, who asked not to be named, said.

Police were deployed in major centres across the country after Khan's arrest, and moved quickly to disperse gatherings of PTI supporters.

Officials said around 35 people were detained in eastern Lahore, and 20 in the port city of Karachi.

In Khyber Pakhtunkhwa, the northern province that has long been a Khan stronghold, authorities said more than 150 PTI supporters had been picked up.

Khan's jailing will do little to calm the economic and political unrest that has roiled the nation for the past 18 months.

"Everyone will ask questions about the credibility of elections in the absence of PTI and Imran Khan and questions will be raised about the credibility of elections in the outside world as well," political analyst Hasan Askari told AFP.

Khan rose to power in 2018 on a wave of popular support, an anti-corruption manifesto, and the backing of the powerful military establishment.

When he was ousted in April last year, analysts said it was because he lost the support of the top generals.

Khan has faced a slew of court cases on charges he says are politically motivated since being ousted.

The case that has led to his imprisonment centres on gifts he and his wife received while in office.

Pakistan newspapers have for months carried lurid stories alleging Khan and his wife received lavish presents worth millions during trips abroad -- including luxury watches, jewellery, designer handbags and perfumes.

Government officials must declare all gifts, but are allowed to keep those below a certain value or buy them at an officially agreed price.