Tech powerhouse Taiwan started phased blackouts islandwide on Thursday after an outage at a coal- and gas-fired power plant hit 6 million homes, as the government worked to resume normal supply by evening.

The world's biggest contract chipmaker, TSMC said some of its facilities suffered a "brief power dip", but power had been restored.

Officials at three major science parks in Hsinchu, Tainan and Taichung, where TSMC and other semiconductor firms all have large operations, told Reuters there was no impact on the operations of the major chipmakers.

In a text message, the government said its grid did not have sufficient electricity capacity after the outage at the power plant in the southern port city of Kaohsiung.

Several cities reported blackouts, the official Central News Agency said, as a top official appealed for calm.

"The government has a grasp of the situation," cabinet spokesman Lo Ping-cheng told reporters. "Citizens please remain calm and there's no need for panic."

All units of the Hsinta power plant in Kaohsiung were shut after an "incident", Lo added, without giving details or identifying the cause of the outage.

Utility Taipower said more than six million homes were hit by the outage, which it blamed on a technical failure at the power plant.

The island's blackouts will run in rotation until 6:20 p.m. (1020 GMT), it said, with a decision on any extensions to be made later.

The economic ministry said it was working to restore supply by evening. The main international airport near Taipei, the capital, and the high speed rail line were operating normally, the transport ministry said.

Fire officials said they were responding to more than 200 reports of people trapped in elevators, most of them in northern Taiwan.