Chinese shipping giant COSCO on Wednesday said it had completed the acquisition of a majority stake in OLP, the company running the main Greek port of Piraeus.

Under the deal, approved by parliament in July, COSCO acquired 67 percent of the port authority for 368.5 million euros ($409 million).

"COSCO Shipping is now the majority shareholder of OLP, taking over the port's management and operations," the company said in a statement.

The sale gives COSCO rights to run Piraeus until 2052.

Leftist Prime Minister Alexis Tsipras had opposed the port's privatisation before coming to power last year.

In July he departed for a six-day trip to China as lawmakers approved the deal.

COSCO was the sole bidder in the process.

OLP said a new 11-man managing board named on Wednesday includes seven Chinese representatives, including the chairman and the CEO.

"This is the first cross-border acquisition by COSCO shipping," the company said.

COSCO, through its Piraeus Container Terminal (PCT) arm, already manages the two main container terminals at the port -- one of Europe's busiest -- under a 35-year concession signed in 2008.

Now it has control of the port, including its passenger ferry functions used by millions of tourists every year heading for the picturesque Greek islands.

COSCO has pledged to invest nearly 294 million euros ($326 million) to expand cruise facilities, upgrade the dockyard and create car space.

The company wants to turn Piraeus into the largest container port in Europe and the world's main cruise departure hub.

The mayor of Piraeus had in the past expressed misgivings about an all-out sale of the port, and local unionists had protested about low wages and working conditions on the COSCO-run docks.