Police and politicians in the east German state of Saxony have been accused of ignoring or underplaying the rising influence of the far right, after an incident involving an off-duty police officer who tried to stop a TV crew filming a rally by the Pegida group in Dresden.

Video footage that has gone viral showed a man later identified as an off-duty police employee shouting at crew members from state broadcaster ZDF. The man, dressed in a sun hat in the colours of the German flag, reported the crew to police, saying they were breaking the law, even though it is not illegal to film a demonstration in Germany. The journalists were then detained for 45 minutes.

The anti-Islam, populist group was demonstrating against a visit by the chancellor, Angela Merkel.

The incident has raised questions about the growth in support for the extremist movement among officials in the state, which is a stronghold for far-right sentiment.

@Frontal21 (@Frontal21) Am Rand des Besuchs der Bundeskanzlerin in Dresden ist ein Kamerateam, das im Auftrag des @ZDF für #Frontal21 https://t.co/t7q5CLkB6t - unterwegs war, etwa eine 3/4 Stunde von der Polizei festgehalten worden.Das Team war vorher von Pegida-Demonstranten verbal angegriffen worden. pic.twitter.com/JEPtFTGoGc

Michael Kretschmer, the prime minister of Saxony and a leading member of Merkel’s Christian Democratic Union, came under fire for appearing to defend the police action. In a tweet – since deleted – he stated: “The only people who come across seriously in this video are the police.”

In a later tweet, he stressed his support for press freedom, writing: “I stated my opinion clearly; it hasn’t changed. Police evaluation shows the matter was dealt with properly. I am a staunch defender of press freedom and a factual debate...”

Michael Kretschmer (@MPKretschmer) Meine Meinung habe ich deutlich gesagt. Sie hat sich nicht geändert. Aufarbeitung der Polizei zeigt Ordnungsmäßigkeit des Einsatzes. Ich bin ein überzeugter Verteidiger der Pressefreiheit und eines sachlichen Meinungsstreits. Den hashtag „Pegizei“ halte ich für unverantwortlich! https://t.co/21VcbHBh3x

There are growing concerns in Germany about the willingness of state employees, particularly the police, to voice rightwing views, most particularly in the former communist east, where criticising the media has become increasingly normal.

Merkel’s decision in 2015 to let in about a million migrants, many fleeing wars in the Middle East, has fuelled support for far-right groups such as Pegida (Patriotic Europeans Against the Islamisation of the West), and Alternative für Deutschland (AfD), now the main opposition party in parliament.

The justice minister in Merkel’s government, Katarina Barley of the Social Democratic party, said on Thursday the events in Saxony were “really worrying”. She added: “The authorities there need to investigate this urgently and thoroughly freedom of press is a vital aspect of our society and is protected by our constitution.”

Cem Özdemir, a leading member of the Greens, said: “Those who are responsible for protecting our constitution have no place at organisations and parties who fight against our constitution – not even in their leisure time.”

Jörg Radek, deputy leader of the main police trade union, said unless Pegida and the AfD were deemed anti-constitutional there was no reason for police not to take part in their activities. But he said he rejected that there was growing evidence of entrenched far-right views within the police.

“I have no knowledge of what’s referred to as the ‘Saxony cesspool’,” he said, “and no understanding for the term ‘Pegizei’,” referring to a mock term for police sympathetic with Pegida, a portmanteau of polizei (police) and Pegida.

The police employee is now on holiday, but will be called in to talk to his seniors about the incident on his return, a spokesman for Saxony police said. There was no indication as to whether he would face disciplinary proceedings.

Thomas Geithner, the head of police in Saxony, rejected claims that his officers had curbed press freedom with their actions. But he said some of the force supported Pegida. “After all, the police is a cross-section of society,” he said. “You can find every political persuasion here.”