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.

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.

Pakistan police said Wednesday they had arrested nearly 1,000 protesters who marched on the capital demanding the release of jailed ex-prime minister Imran Khan, after crowds were evicted from the city centre in a sweeping security crackdown.