Hundreds of protesters gathered outside the legislature's main entrance, some throwing smoke bombs and water bottles at police officers guarding the building in central Taipei.

They also unsuccessfully tried to hurl an empty wooden coffin into the parliament compound's courtyard, television footage showed.

"How can the government unilaterally cut (our pensions) without our consent? The government is lousy, unfair and unjust," said Wu Chih-chang, chairman of the Blue Sky Action Alliance which organised the protest.

A handful of protesters were seen being taken away by police as they tried to climb over the gate, and others tried to pull down the gate using ropes and chains, in a bid to gain entry in an ongoing confrontation.

Proposed pension reductions for military veterans are part of wider cutbacks in Taiwan that have triggered mass street protests as well as clashes inside the parliament among lawmakers.

In February, a protest by military retirees ended in tragedy as a former colonel fell while climbing up a wall, and later died in hospital.

Last week legislators brawled in parliament as a draft bill proposed by the cabinet was being deliberated for the first time, with the opposition Kuomintang (KMT) demanding President Tsai Ing-wen apologise to the veterans.

The backlash over the cuts is a major challenge for Tsai, who has seen her popularity rating fall since her election two years ago.

Legislators passed a separate pension reform bill last June that targeted civil servants, as the government warned it could no longer afford their high-interest deals.

Tsai admitted in a television interview earlier this month that the reforms have "offended many people" but stood by the plan to make the pension system more sustainable.

Taiwan's pension schemes vary for different occupations and public sector retirees typically receive more generous packages than workers from other sectors.

The government has warned that various pension funds could go bankrupt as early as 2020 if the system is not overhauled.