Pakistani security forces pushed a protester off a 25-foot tall stack of shipping containers as they were accused of opening fire on supporters of Imran Khan at a huge demonstration in Islamabad.

Thousands of supporters of Pakistan’s jailed former Prime Minister Imran Khan broke through barricades around the capital Tuesday and marched into Islamabad, clashing with security forces and demanding his release.

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.