Police in Pakistan have fired tear gas and scuffled with stone-throwing supporters of defiant former prime minister Imran Khan.

They had gathered for planned marches towards central Islamabad for a rally Mr Khan hopes will bring down the government and force early elections.

The marches have raised fears of major violence between supporters of Mr Khan – now Pakistan’s top opposition leader – and security forces.

The government of Mr Khan’s successor, Shahbaz Sharif, had banned the rally and warned Mr Khan he could face arrest if he went ahead with the demonstrations.

The country’s Supreme Court ruled later on Wednesday that Mr Khan’s rally could go ahead – but only at specifically allocated public grounds and on condition the demonstrators disperse after an address by the former prime minister.

The court also asked Mr Khan’s lawyer, Babar Awan, to ensure that the rally remains peaceful.

However, Mr Khan persisted, urging supporters to head towards the square near parliament for the rally that he planned would evolve into a sit-in there until the government resigns.

By late evening, the former prime minister had not arrived in Islamabad while police were making security arrangements for an alternate location for the rally, far from the parliament building.

Earlier in the morning, riot police fired tear gas and pushed back hundreds of demonstrators who hurled stones as they tried to pass a roadblocked bridge near the city of Lahore to board busses bound for the capital, Islamabad.

A dozen demonstrators and several police officers were injured. Altercations between the police and Mr Khan’s supporters were also reported elsewhere.

Pakistan Politics
Shipping containers placed by authorities block a key road route to the capital city (AP)

Ahead of the marches, authorities used dozens of shipping containers and trucks to block off major roads into Islamabad.

Mr Khan, a former cricket star turned Islamist politician, served as prime minister for more than three years until last month, when he was ousted by a no-confidence vote in parliament. Since then, he has held rallies with thousands of people across the country.

Mr Khan says his removal from office was the result of a US-organised plot and collusion with Mr Sharif, whose government has vowed a stern response if Mr Khan violates the ban. Washington has also denied any role in Pakistan’s internal politics.

Despite the ban, Mr Khan insisted his rally would be massive and peaceful – and continue until the government agrees to hold fresh elections this year, not in 2023 as scheduled. Organisers had planned for crowds to travel by car and bus to Islamabad’s city limits, then march on foot.

Mr Khan himself travelled by helicopter to a road some 62 miles north-west of Islamabad, where he condemned the police crackdown and urged supporters to join the rally.

“My message for the nation: Everyone must break out of the grip of fear to achieve freedom,” he wrote on Twitter, before starting out by vehicle. His convoy still faces a series of roadblocks ahead that would require heavy machinery to remove.

Mr Khan has urged his supporters to remove the containers that were filled with earth and circumvent any blockades in order to enter the city. “I will be among you Wednesday afternoon,” he had vowed on Tuesday.

Shipping container blocks road
Mr Khan has pledged the demo will be peaceful (AP)

Thousands of Mr Khan’s supporters along with leaders of his Tehreek-e-Insaf party had already massed in Peshawar, the capital of the north-western Khyber Pakhtunkhwa province where his party rules. From there, his followers must cross a bridge at the province’s border that the government has blocked, before assembling on the outskirts of Islamabad.

The government launched a crackdown and arrested more than 1,700 Khan supporters, according to interior minister Rana Sanaullah. He congratulated his countrymen for rejecting the rally by not participating in it and apologised for the inconvenience caused to citizens due to the blockades.

“Imran Khan had claimed that he would gather two million people here in Islamabad today, but he is marching towards Islamabad along with only 6,000 or 7,000 demonstrators,” he told a news conference on Wednesday. “We are fully prepared to handle him.”

Authorities have deployed additional police and paramilitary troops on highways and in Islamabad, with tractor trailers also parked across both lanes of traffic in several areas.

The measures were announced after a police officer was killed during a raid on the home of a notable Khan supporter in Lahore.