The EU's top court has ordered Poland to "immediately suspend" the application of its law which lowers the retirement age of Supreme Court judges.

The European Court of Justice upheld the request by the European Commission and the head of Poland's ruling party said it would comply with the decision.

The Polish government has been accused of trying to appoint loyal judges.

But Warsaw argues the reforms, which lower the retirement age from 70 to 65, make the court more efficient.

Poland has clashed with EU bodies in recent months over a number of issues.

"We are members of the European Union and we will abide by European Union law," said the head of the ruling Law and Justice party (PiS), Jaroslaw Kaczynski, adding that Poland "had the right to appeal".

What did the ECJ ruling say?
The Luxembourg-based court ordered Poland to immediately reinstate the Supreme Court judges who have been forced to retire since the new law came into force in July.

The ECJ said its decision was an interim measure in response to a European Commission request, and a final ruling would be issued at a later date. Poland has yet to make a submission in the case.

About a third of the judges have stepped down, but Chief Justice Malgorzata Gersdorf - who is also affected by the changes - is refusing to quit, saying the Polish Constitution guarantees her a six-year term.

Fines could be imposed if Poland is found in breach of EU law.

The judicial reforms triggered mass street protests across Poland.

Opponents say the governing Law and Justice (PiS) party will use the law to appoint new judges loyal to the authorities.

The conservative government denies the accusations, saying the country's judiciary was not properly reformed after the end of communism in 1989.

After Friday's order, Prime Minister Mateusz Morawiecki has said "several possibilities will be analysed" - without giving details.