A Chinese automaker backed by billionaire US investor Warren Buffett has signed an agreement with energy giant Bulmineral to build an electric bus and car factory in Bulgaria, a report said Wednesday.

China's Build Your Dreams (BYD) and Bulgaria's Bulmineral will build the factory in the town of Breznik, some 50 kilometres (31 miles) west of Sofia, and will produce 40-60 electric buses per day, the energy firm's CEO Alexander Usachev told Xinhua.

The factory's car-making capacity will be determined in three months, added Usachev.

The investment cost was not mentioned in the report.

Ho Isbrand, a BYD official in Europe, said he was happy the Bulgarian firm was helping the Chinese company develop its business in Europe, according to Xinhua.

BYD is listed on the Hong Kong stock exchange with Buffett a minority shareholder.

It is the second Chinese auto firm to expand to Bulgaria after Great Wall Motor, which in February launched an assembly plant in Europe in the northern town of Bahovitsa.

After its completion around 2015, the Bahovista plant is expected to make 50,000 vehicles annually.

China is the world's largest car market. Seventy percent of cars sold are foreign brands.