The Chinese government will impose additional tariffs on a type of plastic made in Taiwan starting Saturday. Commerce ministry officials say prices are unfairly low.

The announcement came on Friday. The ministry plans to slap anti-dumping duties of 9 to 22.4 percent on Taiwanese polycarbonate exports over the next five years.

The material is used in car parts and electronic devices.

Observers say Beijing is attempting to ramp up pressure on Taiwan's President-elect Lai Ching-te, who will take office on May 20.

Also on Friday, Chinese aviation authorities started operating a commercial flight route that passes near Taiwan's remote Kinmen and Matsu islands.

And in February, they replaced an existing flight route with another that flies closer to Taiwan.

Leaders in China apparently want to undermine an unofficial median line in the Taiwan Strait designed to prevent accidental clashes between the two sides.