Uber -- the app-based car service -- has raised $1.2 billion to keep expanding Uber China, a source close to the efforts said.

The fundraising round has not yet been completed, and hundreds of millions more should still be added, the source said.

The source confirmed US media reports that Chinese Internet search giant Baidu took part in this round.

Baidu has been an Uber investor since last year; in December it said it had made a strategic investment of about $600 million in the American company.

Uber has been maintaining an aggressive international expansion plan despite fierce opposition in some countries from regulators and established taxi industry players.

San Francisco-based Uber says it operates in some 250 cities and 58 countries.

Its app, using a geolocator, allows users to connect with drivers and bypass traditional taxi services.

Despite its spectacular growth, Uber -- which has reached a value of $50 billion -- has faced troubles in many countries. The company decided to suspend its low-cost service in France after a nationwide taxi strike in protest against Uber turned violent.

Didi Kuaidi, Uber's main rival in the massive Chinese transport market, is close to raising $3 billion from investors, Bloomberg reported.

Reached for comment in Beijing early Tuesday, Didi Kuaidi declined to confirm or deny the reports.