Authorities have reopened roads linking Pakistan’s capital with the rest of the country, ending a four-day lockdown, after using tear gas and firing into the air to disperse supporters of imprisoned former Prime Minister Imran Khan who demanded his release from prison.

The demonstrators want the federal government to resign over what they call rigged general elections this year.

Prime Minister Shehbaz Sharif denounced the attack, saying an “anarchist group” was deliberately targeting law enforcement personnel.

Mr Khan’s Pakistan Tehreek-e-Insaf (PTI) said a “massacre” unfolded in Pakistan and the armed forces fired live rounds, killing “hundreds of people” and many injured with gunshot wounds. It did not give a number as to how many were killed.

Supporters of the ex-prime minister marched toward Islamabad, the capital. Clashes with the police left at least one officer dead, the authorities said.

Thousands of Imran Khan supporters marched closer to the capital of Islamabad on Monday demanding his release from prison as authorities braced to prevent the crowd from entering the city.