US cable company Liberty Global augmented its stake to 28.5% in Ziggo, a Dutch cable operator, a Reuters report said.

Liberty used to own 12.65% of Ziggo after previous owners Warburg Pincus and Cinven left. Liberty subsequently increased its stake to 15%, the report said. According to Dutch law, Liberty would have to make a bid to fully acquire Ziggo once its stake reaches more than 30%

In a statement, Ziggo said: "The supervisory board and the board of management will continue to act in the best interests of its stakeholders in assessing steps made by Liberty Global while continuing to focus on executing Ziggo's strategy."

Shares of the Dutch cable operator dropped about 10% after Ziggo announced that it is going to slash its profit outlook for this year.

Incidentally, Liberty also owns stocks in UPC, Ziggo's main rival, as well as a majority stake in the Belgian operator Telenet.