Chen added that the orders provided solid evidence "that made-in-China electric buses are not low-quality goods".

"We Chinese hold a competitive edge over our peers from developed countries in this particular high-end category."

BYD recently gained the important EU "Whole Vehicle Type Approval" which allows it to sell its electric buses in all EU member states.

"The competition in western regions is always high. The east is easier with less restrictions, and certainly, expansion into the east provides us with much easier access to the whole of Europe," said Chen.

BYD plans to first sell its Bulgarian-made electric buses locally, then to neighboring European countries.

"The well-educated workforce and lower factory wages" of eastern European nations make them very attractive," he added.

"We don't exclude the possibility of establishing similar plants in other east European nations, such as Hungary."

China's investment interest in East Europe has actually come late compared with some other regions of Asia and Africa.

According to Ministry of Commerce figures, China's cumulative investment across the 10 main central and eastern European countries had reached $830 million by the end of 2010, accounting for just 6.6 percent of its total EU investment at the time.

Poland, Hungary and Romania were the major destinations, accounting for nearly 90 percent of total Chinese investment in the region.

But over the past two years, Chinese interest in eastern Europe has grown considerably, through direct investment and mergers and acquisitions.

Last February, Guangxi Liugong Machinery Co Ltd, for instance, took over Huta Stalowa Wola, a Polish road machinery maker, for about $100 million, marking China's biggest investment to date in Poland.

The same month, Chinese automaker Great Wall Motor Co Ltd developed China's first automotive project in the EU by opening an assembly plant in northern Bulgaria.

In late April, during a visit to Poland, Premier Wen Jiabao said that a $10 billion special credit line would be provided for joint investment infrastructure and technology projects in the east European country.

Shortly after that, Vice-Premier Li Keqiang visited several European nations, including Russia and Hungary.