A record heat wave engulfing parts of China has prompted authorities in the inland province of Sichuan to extend its restriction on industrial power usage.

The authorities had ordered companies that use large amounts of electricity to suspend production at their factories until last Saturday to address electricity shortages. Chinese media say there was a notice of an extension until Thursday.

Some businesses are trying to overcome the situation with in-house power generation. They include Japanese firms such as Toyota Motor, which has a plant in the city of Chengdu in the province.

The city subway has set air-conditioners at higher temperatures and commercial facilities have turned off lights to save electricity.

The mercury topped 40 degrees Celsius in Sichuan and the city of Chongqing on Sunday. Chinese media say temperatures hit new highs at more than 200 observation points over the past month.

Power-usage restrictions are expected to remain in place until Wednesday in Chongqing. Panasonic has halted operations at its plant in the city.

Concerns are rising as many automobile- and semiconductor-related firms are located in Sichuan and Chongqing, although the extreme heat is forecast to ease from the middle of this week.