A pro-Palestinian activist climbed the flagpole outside Berlin's Reichstag building on Sunday and replaced Germany's national flag with a Palestinian flag, in an incident that drew condemnation from politicians and an investigation by police.

At around 11:15am, a 22-year-old man used climbing gear to scale the nearly 30-metre pole in Platz der Republik, in front of the building that houses Germany's federal parliament, the Bundestag. He removed the 60-square-metre German flag and threw it to the ground before raising a Palestinian flag in its place. Two other men, aged 20 and 32, remained below and filmed the incident, which was livestreamed on TikTok.

Police and firefighters were called to the scene. The Palestinian flag flew for about an hour before the activist climbed down on his own at around 12:30pm, and firefighters removed the flag a few minutes later. Police detained three men in connection with the incident. All three are German citizens, and a 20-year-old suspect was later released.

The flag that was taken down is known as the Flag of Unity. It commemorates Germany's reunification on 3 October 1990, after the fall of the Berlin Wall, and the flagpole is designated a national monument. Because of its special symbolic status, it is exempt from the usual rules requiring national flags to be flown at half-staff during national mourning, though it is lowered on exceptional occasions.

Police opened a criminal investigation into suspected offences including denigration of the state and its symbols, property damage, violations of the law governing public assemblies, and trespass. The State Security Division of the Berlin State Criminal Police Office is conducting the investigation.

A pro-Palestinian group called Peacefully Against Genocide claimed responsibility for the action. The group said it was meant to show solidarity with people in Palestine and to protest against German politicians' failure to act against grave human rights violations, and it opposes German arms deliveries to Israel. According to reports, the group staged a similar action last year, when activists climbed onto the Brandenburg Gate and unfurled a banner with pro-Palestinian messages.

The incident drew sharp criticism from German politicians. Bundestag President Julia Klöckner described the act as unbelievable in an interview with Bild and demanded stronger protection for the parliament. Wolfgang Kubicki, leader of the liberal Free Democratic Party, said the perpetrators wanted to sow discord in the country and trample on the republic's liberal democratic values.

Israel's ambassador to Germany, Ron Prosor, also condemned the act, saying that replacing the German flag with a Palestinian flag amounted to rejecting the values represented by Germany's national colours: freedom, democracy and the rule of law. The Israeli Embassy in Berlin said anyone who raised the Palestinian flag in Berlin while taking down the German flag made it unequivocally clear that they opposed everything black, red and gold stand for.

The incident came just one day before Germany and the world mark the 88th anniversary of Kristallnacht, the night of anti-Jewish pogroms in 1938. The timing added to the sensitivity of an act targeting one of the country's most recognisable national symbols.