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.

Forcing their way into Islamabad after pushing the security forces on backfoot in violent clashes that resulted in at least half a dozen deaths earlier in the day, thousands of Pakistan Tehreek-e-Insaf (PTI) protestors have reached Islamabad's Zero Point 'D-Chowk' where they plan to hold an indefinite sit-in until party chief and former Pakistan Prime Minister Imran Khan is released from jail.

Pakistani protesters demanding the release of ex-prime minister Imran Khan on Tuesday killed four members of the nation's security forces, the government said, as the crowds defied police and closed in on the capital's centre.

Thousands of security forces poured into central Islamabad in an attempt to quell protests in support of Khan that have gripped the capital.

Police in Pakistan clashed with thousands of Imran Khan supporters as they marched towards the capital Islamabad to demand his release, defying a lockdown and a ban on rallies. The former Pakistani prime minister has been in jail for over a year on more than 150 criminal charges.

Four members of Pakistan’s security services were killed as thousands of ex-Prime Minister Imran Khan's supporters clashed with law enforcement in Islamabad.

Thousands of supporters of Pakistan's jailed former Prime Minister Imran Khan marched on the capital Islamabad this week, breaking through barricades and clashing with police in response to his call for a sit-in protest.

Supporters seeking the release of imprisoned Pakistani former Prime Minister Imran Khan on Tuesday broke through a ring of shipping containers locking down the capital, Islamabad, while at least six people have died in protest-related violence.