SHENZHEN, China  - Toyota Motor has halted production on some ageing lines at a joint venture in China while operations continue as normal, the Japanese automaker said on Saturday after a media report that it was partially suspending production due to weak sales.

The production halt at the Tianjin venture with China's FAW was a planned move, and Toyota is adjusting production based on "changes in the composition of vehicle models", a spokesperson said by email.

"The reason for stopping the production line was to optimize the production system in consideration of aging and changes in the composition of vehicle models such as body types."

Japan's Jiji news service said on Friday the world's largest automaker by sales was suspending some production as part of a major production adjustment in response to weak sales of gasoline-engine cars.

A FAW representative did not respond to a request for comment.

Reuters reported last month that Toyota had told dealers it would extend a plan to reduce output at the FAW venture.

Slowing sales pose a growing challenge to Toyota in China which accounted for nearly a fifth of Toyota's worldwide sales of about 8.5 million vehicles over the first 10 months of the year, including sales of its luxury Lexus brand.

(Reporting by David Kirton in Shenzhen and Brenda Goh in Shanghai)