MANNHEIM, Germany -- A car drove into a crowd in the western German city of Mannheim on Monday, killing at least two people and injuring 11 others, overshadowing carnival celebrations in the region where police had been on alert for attacks.

Police detained the driver, who appeared to have ploughed intentionally into the crowd given the speed at which he was driving, prosecutors said in an act Interior Minister Nancy Faeser labeled "horror in broad daylight".

He did not appear to have been politically or religiously motivated, but there were reasons to believe he was psychologically unwell, said Mannheim Chief Public Prosecutor Romeo Schluessler.

Prosecutors have initiated investigative proceedings against the suspect, a 40-year-old German man from the neighbouring state of Rhineland-Palatinate, on two counts of murder and multiple counts of attempted murder.

The suspect has not been questioned yet as he had to undergo medical treatment after shooting himself in the mouth with a blank-firing gun after the attack.

He appeared to be a landscape gardener who lived alone, prosecutors said, adding that they were now investigating his home for clues.

Security has been a key concern in Germany following a string of violent attacks in recent weeks, including deadly car rammings in Magdeburg in December and in Munich last month, as well as a stabbing in Mannheim in May 2024.

"The incident — like the terrible acts of the past months — serves as a stark reminder: we must do everything possible to prevent such acts," said Germany's likely next leader, Friedrich Merz, whose conservatives won a national election last month.

"Germany must once again become a safe country. We will work with full determination to achieve this."

Messages of solidarity were sent from across Europe.

"To all the people of Mannheim, especially to all the relatives of the victims of the attack, to the German people. France is at your side," French President Emmanuel Macron wrote on the social media platform X.

Italy's Prime Minister Giorgia Meloni said "attempts to destabilize democratic nations will not prevail".

The two who died were an 83-year-old woman and a 54-year-old man.

Nervous carnival

Police were on high alert for this year's carnival parades after social media accounts linked to the Islamic State militant group called for attacks on the events in Cologne and Nuremberg.

There did not appear to be a connection between Monday's incident and the carnival celebrations, the interior minister of the state of Baden-Wuerttemberg, Thomas Strobl, told reporters. Those festivities culminated on Rose Monday with a number of parades, although not in Mannheim, which held its main event on Sunday.

Rose Monday, the culmination of the annual carnival season celebrated in Germany's mainly Catholic western and southern regions, features parades of floats that often include comical or satirical references to current affairs.

This year's carnival has included floats featuring U.S. President Donald Trump, Russian President Vladimir Putin, tech billionaire Elon Musk and Ukrainian leader Volodymyr Zelenskiy.

Dressed in traditional jester costumes and sporting colourful makeup, thousands of partygoers danced through the streets of Cologne, Dusseldorf and other cities in western and southern Germany ahead of the fasting season of Lent.