At least six people have died in protest-related violence as supporters seeking Imran Khan’s release from prison broke through barriers meant to lock down Islamabad.

Thousands of opposition protesters have converged on Pakistan's heavily-barricaded capital, demanding the release of jailed former prime minister Imran Khan.

Pakistan deployed the army amid a tense stand-off with Khan's supporters from his Pakistan Tehreek-e-Insaf (PTI) pushing forward by removing hurdles on their way to Islamabad's D-Chowk venue as the government vowed to foil their attempt 'even if a curfew needs to be imposed.