Chinese e-commerce group Alibaba, U.S. online retailer eBay Inc, and private equity firm CVC Capital Partners are among the bidders for Eastern Europe's No.1 auction website Allegro from South Africa's Naspers, sources said.

A deal worth between 2 and 3 billion euros ($2.2-3.3 billion), is expected by the end of the year, market sources said. Polish online groups Wp.pl, owned by Innova Capital, and Onet.pl, controlled by Ringier Axel Springer could also be interested, some of the sources said.

"Allegro is a ready-made entry not only to Poland, but also the region," one market source told Reuters. "Strategic bidders eBay and Alibaba will be hard to beat in the race, with Alibaba looking better positioned from the anti-monopoly point of view."

The Polish e-commerce market, worth more than 32 billion zlotys ($8 billion) with around 22,000 online shops, is set to double in value by 2020, especially given the government plans not to levy online shopping with Poland's new retail tax.

With over 14 million clients, Allegro is competing with local rival and also Naspers-owned OLX.pl, as well as eBay or U.S. Amazon.

Founded in 1999, Allegro is the largest e-commerce investment for Naspers - Africa's largest company by market value - since its acquisition in 2008.

Naspers has transformed itself from an apartheid-era publisher into a $65 billion Internet powerhouse by focusing on e-commerce in emerging markets.

It operates in over 130 countries with stakes in Russian internet group Mail.Ru Group and China's biggest social network and online entertainment firm Tencent Holdings.

It raised $2.5 billion in December last year to fund acquisitions.

Naspers and CVC declined to comment, while Alibaba, eBay, and Allegro were not immediately available for comment.

($1 = 0.9097 euros)

($1 = 3.9833 zlotys)