Toyota is planning to build a new plant in northern China as the world's top automaker ramps up investment after a two-year freeze.

Proposals for the plant in Tianjin -- due to open in 2018 at the earliest with a capacity of 100,000 cars a year -- should be finalised by the summer, Jiji Press and Kyodo News agency reported, according to AFP.

The news comes after reports that Toyota is planning to invest a combined $1.3 billion to build new plants in the Chinese city of Guangzhou and Guanajuato, Mexico.

The Japanese carmaker began operating a new Thai plant in 2013, but since then it has halted investment as the global car market has struggled with oversupply and weak demand.

At the new plant, Toyota will likely produce fuel-efficient passenger vehicles under a local brand through a joint venture with a Chinese firm, the reports said.

The vehicles would meet stricter environmental regulations in China, where air pollution is a serious social problem.

Toyota kept its title as the world's biggest automaker last year as it announced record sales of 10.23 million vehicles, outpacing General Motors and Volkswagen.