BRUSSELS, Feb 8 (Reuters) - EU antitrust chief Margrethe Vestager on Thursday voiced doubts as to whether Big Tech will fully comply with landmark EU rules aimed at reining in their power and ensure a level playing field for smaller rivals.

"I have reservations as to whether or not we will have full compliance," Vestager told a news conference, a sign that she may open investigations into some of the companies in the coming months.

Alphabet's Google, Apple, Amazon , Meta Platforms, Microsoft and ByteDance will have to adapt their core platform services to comply with the Digital Markets Act (DMA) on March 7.

The six companies have been designated as gatekeepers under the DMA. Vestager said she hoped the companies will listen to feedback from third parties on their proposals on how to comply with the DMA and assess changes. (Reporting by Foo Yun Chee)