The European Union has warned Hungary over its media freedom, adding to mounting international pressure over controversial Hungarian legislation changes and practices.

The EU's digital agenda commissioner, Neelie Kroes, wrote to Hungarian Justice Minister Tibor Navracsics overnight into Wednesday to "stress that the respect of media freedom and media pluralism is not only about the technically correct application of EU and national law."

It is "also, and more importantly, about implementing and promoting these fundamental principles in practice," she added, warning that the European Commission "will remain particularly vigilant on those aspects."

The EC letter followed the non-renewal of broadcasting licenses held by the liberal commercial radio station Klubradio, which is known for its critical stance towards the Hungarian government of Prime Minister Viktor Orban.

"Why we sent the letter now? Obviously Mrs Kroes has an ongoing concern and we have been receiving information in recent days suggesting we might have a reason for increasing concern," her spokesman, Ryan Heath, told reporters in Brussels, as cited by DPA.

In an earlier email, he had also pointed to continuing domestic and international criticism of "the risks of disproportionately centralized control of media under Hungary's media law."

The law was amended under pressure from the commission, but it remains "without precedent in other EU jurisdictions," Heath noted.

"The (EU) Charter of Fundamental Rights is very clear: you have to respect media freedom and pluralism. We are closely looking at the situation. We are not dropping the ball," he said.

Hungary is already facing three infringement proceedings from the European Commission over recently approved reforms that affect its central bank, its data protection authority, and its judiciary.

The EU has recently also delayed the launch of aid talks with the cash-strapped country, rapped Budapest over its excessive government deficit, and ordered it to reclaim illegal state aid to national airline Malev, DPA reminds.