BRUSSELS (Reuters) - The European Commission on Thursday stepped up a legal battle with Hungary over EU migration rules and denounced as illegal its “Stop Soros” law that criminalizes support for asylum seekers.

The move will further sour Brussels’s relations with Hungarian Prime Minister Viktor Orban who has been one of the strongest opponents of EU decisions for greater cooperation among EU states to handle the migration crisis.

The EU executive said in a statement that it had referred Hungary to the EU Court of Justice “for non-compliance of its asylum and return legislation with EU law”.

Two EU legal requests went unheeded. This is the third step of a legal procedure that could ultimately lead to financial sanctions on Budapest if the court confirms the commission’s line.

Brussels says the Hungarian authorities have failed to provide effective access to asylum procedures for migrants. Asylum seekers are also held in “transit centers” for more than the maximum stay of four weeks allowed under EU rules, Brussels said.

“The Commission considers that the indefinite detention of asylum seekers in transit zones without respecting the applicable procedural guarantees is in breach of EU rules,” it said in a statement.

Budapest is also in breach of EU rules that require certain guarantees for migrants who are sent back to their countries of origin or transit. Under the Hungarian legislation, “migrants risk being returned without the appropriate safeguards,” the commission said.

No “Stop Soros”

The Commission also chided Hungary over a new law that introduces criminal sanctions for organizations providing assistance to migrants for their asylum and residence applications.

The law, labeled “Stop Soros” because it hits non governmental organizations supported by the U.S. billionaire George Soros, has already been criticized by European rights bodies.

The Commission decided to open an infringement procedure against Hungary saying the new rules curtailed asylum applicants’ right to turn to national, international and non-governmental organizations for help.

The “Stop Soros” bill also introduces new criteria to submit asylum applications which are not in line with EU rules as they limit asylum seekers’ rights, the commission said.

The EU executive sent a “letter of formal notice” to Hungary about the “Stop Soros” law. This is the first step of EU legal proceedings against a member state. Hungary has two months to reply to the Commission’s concerns.