Thousands in Hungary protest against Prime Minister Viktor Orban's controversial new labour law

Thousands of people protested in Hungary against a controversial new labour law and the rule of right-wing Prime Minister Viktor Orban.

Sunday's protest, called "Merry Xmas Mr Prime Minister" by organisers, was the fourth and biggest demonstration in a week by leftist opposition parties, student groups, trade unions and ordinary people against the nationalist government.

Protesters waved Hungarian and European Union flags in Budapest as they walked from Heroes' Square towards parliament in crisp winter weather. They held up banners and shouted slogans including "Don't steal" and "Independent courts".

Citizens in cities outside the capital such as Gyor, Szeged, Miskolc and Debrecen demonstrated for the first time on Sunday.

The unrest was sparked after opposition parties blew sirens and whistles inside parliament on Wednesday in an unsuccessful effort to prevent the adoption of two controversial bills.

A labour code change dubbed the "slave law" by its critics hikes the maximum annual overtime hours for workers and extends the time period for calculating and paying overtime to three years.

Trade unions say the changes were made at the behest of large international manufacturing companies and could expose workers to exploitation, as well as delays in overtime payments.

According to the government, the law will benefit both those wanting to work more hours and employers who need more manpower as the economy struggles with labour shortages.

Also passed by parliament, which is dominated by Orban's ruling party, was a bill paving the way for new "administrative courts" to oversee public administration cases such as public procurements or election procedures.

Justice Minister Laszlo Trocsanyi, a close Orban ally, will oversee the courts, leading some to warn of near-total political influence over the judicial system.

Anger over the legislation has prompted various opposition parties, who accuse Orban and his Fidesz party of steering Hungary towards authoritarianism, to join forces during the protests.

Pro-government public and commercial media have portrayed the protesters as anarchists and "mercenaries of George Soros".

The Hungarian-born billionaire Soros from the United States has long been accused by Orban of plotting to import migrants into Europe and destabilise Hungary.