Waving placards reading "nuclear go zero," and "abolish nuclear, save Taiwan," protesters rallied outside the presidential office in Taipei on the same day as Japan marked the seventh anniversary of the Fukushima disaster.

Protesters were worried by a recent decision by the cabinet-level Atomic Energy Council to allow state-owned energy company Taipower to restart a reactor at a facility near Taipei, pending parliament's final approval.

The reactor has been offline since May 2016 after a glitch was found in its electrical system, which the company said has since been resolved.

Anti-nuclear groups are now questioning whether President Tsai Ing-wen's Democratic Progressive Party (DPP) will keep its promise to phase out nuclear energy.

"It would be violating the spirit of creating a nuclear-free homeland by 2025 pledged by the DPP," said Tsui Shu-hsin of the prospect of restarting the reactor. Tsui is spokeswoman for Nuclear Go Zero Action Platform which organised the rally.

Lawmaker Huang Kuo-chang, head of the opposition New Power Party, echoed the sentiment.

"The government should move forward, not backwards and restarting the reactor would be a regression," he told reporters at the rally.

Taiwan currently generates about one-fifth of its energy from three nuclear plants.

Although concerns have grown over power supply sufficiency following massive power failures across the island in August last year, many in the island remain adamantly against nuclear energy.

In 2014, authorities were forced to seal off a nearly-completed fourth nuclear plant after public opposition.

Some at Sunday's rally wore sunflowers on their hats to symbolise clean energy.

"I would rather the government restrict the use of electricity than relying on nuclear energy which is unsafe and generates a lot of waste," said 22-year-old college student Yao Hsing-yu.

Taiwan started annual anti-nuclear rallies to commemorate Japan's nuclear disaster on March 11, 2011 when the Fukushima energy plant was hit by a tsunami following an earthquake, knocking out power to its cooling systems and sending reactors into meltdown.

Taiwan, like Japan, is prone to frequent quakes as the island lies on a number of fault lines.

Last month, 17 people were killed and nearly 300 injured when a 6.4 magnitude quake hit eastern Hualien, leaving almost 2,000 buildings damaged.

"Nuclear facilities are unsafe as Taiwan has many earthquakes. The government needs to take the lead to actively develop alternative and green energy," said 40-year-old protester Fan De-lu.