Pakistani police fired tear gas and engaged in scuffles with stone-throwing supporters of defiant former Prime Minister Imran Khan as they prepared for planned marches toward central Islamabad on Wednesday for a gathering he believes would bring down the government force early elections.

The marches have sparked worries of massive bloodshed between Khan's supporters – currently the most prominent opposition leader in Pakistan – and security personnel. The government of Khan's successor, Shahbaz Sharif, banned the march and warned Khan that he could be arrested if he proceeded with the protests.

Earlier in the morning, riot police fired tear gas and pushed back hundreds of stone-throwing protesters attempting to pass a barrier near the city of Lahore to board buses going for the capital, Islamabad.

Twelve demonstrators and multiple police officers were hurt. Also reported were altercations between the police and Khan's supporters elsewhere.

Major routes leading into Islamabad were blocked with dozens of shipping containers and trucks before Wednesday's demonstrations.

A former cricket star turned Islamist politician; Khan served as prime minister for more than three and a half years before being dismissed by a vote of no confidence in Parliament last month. Since then, he has participated in rallies with tens of thousands of people.

Khan asserts that his expulsion from office resulted from a U.S.-organized conspiracy and Sharif's collaboration; Sharif's government has threatened a severe response if Khan breaks the ban. Washington has likewise denied any involvement in the domestic politics of Pakistan.

Despite the restriction, Khan insists his gathering will be significant and peaceful — and continue until the government agrees to hold fresh elections this year, not in 2023 as intended. The plan was for the multitudes to travel by car and bus to the city boundaries of Islamabad, then march on foot.

Khan traveled by helicopter to a highway approximately 100 kilometers (62 miles) northwest of Islamabad, where he denounced the police crackdown and asked followers to join the march.

"My message to the nation: Everyone must overcome fear to achieve freedom," he posted on Twitter before departing from the Swabi interchange in a car. His convoy still encounters several barriers that can only be removed with heavy gear.

Khan has asked his supporters to remove the earth-filled containers and avoid any roadblocks reaching the city. On Tuesday, he had promised, "I will be with you Wednesday afternoon."

Thousands of Khan's fans and leaders of his Tehreek-e-Insaf party had already gathered in Peshawar, the provincial capital of Khan's Tehreek-e-Insaf-controlled province in the province's northwestern Khyber Pakhtunkhwa region. From there, his followers must pass a government-blocked bridge at the province's border before gathering on the outskirts of Islamabad.

According to the Interior Minister Rana Sanaullah, the authorities initiated a crackdown and arrested nearly 1,700 Khan loyalists. He praised his compatriots for rejecting the rally by not attending, and he apologized for the trouble the blockades had given the citizens.

"Imran Khan had claimed that he would bring 2 million people to Islamabad today, but he is marching toward Islamabad with only 6,000 or 7,000 protesters," he said at a news conference on Wednesday. We are entirely prepared to deal with him.

Authorities have deployed more police and paramilitary forces on highways and throughout Islamabad, along with tractor-trailers blocking both lanes of traffic in several locations.

The measures were announced following the death of a police officer during a raid on the Lahore home of a prominent Khan supporter.

On Wednesday, the Supreme Court of Pakistan heard a plea to remove the blockades into Islamabad. According to the authorities, the government may consider revoking its prohibition if Khan provides written assurance that his protest will be peaceful and confined to a public park.

Later in the day, the court was anticipated to issue an order about Khan's protest.