The Reichstag is a magnet for tourists because it brims with German history. The meeting place of the Imperial Diet, it was torched in 1933 in a calamity that quickened Hitler's rise and wasn't reconstructed until after reunification more than half a century later.

On Saturday, according to police, two Chinese tourists standing outside the building began giving Nazi salutes. They were briefly detained, accused of violating a German law that seeks to keep the Reichstag's darkest chapter from repeating itself.

The salute - with the right arm straight and angled slightly up, palm down - was used as a greeting and a way of expressing devotion to Hitler under the Third Reich. The German Constitution, approved after the Second World War, makes it a criminal offense, along with Holocaust denial and other symbols and signals associated with the Nazis.

Several other European nations also ban the gesture. Switzerland's Supreme Court last week upheld the conviction of a man who had performed the "Heil Hitler!" salute outside a synagogue in Geneva.

Police guarding the Reichstag, which today is the seat of the lower house of the German Parliament, saw the two tourists, aged 36 and 49, taking photographs of each other giving the salute, according to a police statement.

The two men were taken to a nearby police precinct and questioned. They were released on bail of 500 euros, or nearly $600, each.

A criminal investigation will continue, though the tourists are being permitted to leave the country with their tour group, a police spokeswoman said Sunday. Conviction can carry a prison sentence of up to three years.

In 2011, a 30-year-old Canadian tourist was detained after being photographed giving the Nazi salute outside the Reichstag. He got off with a fine.

The burning of the Reichstag shortly after Hitler's selection as chancellor in 1933 was used by the Nazis as an excuse to solidify their power. They blamed a Dutch Communist for setting the fire.

The rules wiping away relics of the Nazi past are sacrosanct in Germany - taught in schools and emphasized in households. But it is not clear how familiar foreign visitors are with the postwar constitutional statute, typically used to prosecute members of the far right.

European capitals are popular destinations for tourists from China, and states such as Germany eagerly court these visitors. Next year has been dubbed the EU-China Tourism Year, part of an initiative developed by the president of the European Commission, Jean-Claude Juncker, and the Chinese prime minister, Li Keqiang.

For several years now, the government in Beijing has expressed growing concern over embarrassing behavior by Chinese tourists traveling abroad, and has tried to persuade travelers to respect local laws and customs.