German Authorities Confirm Manhunt for Tunisian Man Wanted Over Berlin Attack Authorities said the suspect is a 24-year-old Tunisian.

BERLIN, Germany -- The Berlin truck attacker was still on the run Wednesday morning, and authorities warn that the suspect is likely armed.

In a notice published online Wednesday, Germany's federal prosecutor identified the suspect as 24-year-old Anis Amri, who was born in Tunisia. A reward of 100,000 euros is being offered for information leading to his arrest. German authorities believe he is still in the country and may be armed and dangerous.

Germany's federal interior minister emphasized to reporters that the man was a suspect and not necessarily the perpetrator.

"We are still investigating in all directions," Thomas de Maiziere said in a news briefing.

Ralf Jaeger, the interior minister of the German state of North Rhine–Westphalia, told reporters earlier during a televised press conference that a Europe-wide manhunt is underway for the suspect, who had known ties to radical Islam and was classified as a threat by several security agencies. Jaeger didn't say whether the suspect was previously detained by authorities.

According to Jaeger, the suspect lived in the town of Kleve in North Rhine–Westphalia before moving to Berlin, Germany's capital, in February. His application for asylum was rejected in June, but he could not be deported because he had no valid papers, Jaeger said. He did not provide the suspect's name or birthdate.

ISIS took responsibility for Monday's attack, claiming the suspect is "a soldier of the Islamic State," according to a statement released by the terrorist group's Amaq News Channel.

On Tuesday night, German prosecutors released a man they had arrested in connection to the attack because of insufficient evidence. The man was a 23-year-old Pakistani asylum seeker, police said.

In the back of the Polish-owned tractor-trailer used in the attack, its Polish driver was found dead with gunshot wounds. No gun was recovered at the site, suggesting that the weapon used may still be with the attacker.

As the manhunt intensifies, police are asking eyewitnesses to come forward with any information. Police said they have received 508 tips so far, 80 of which they deem "serious."

Police are warning the public to be extra vigilant not only in Berlin but also elsewhere across Europe, where thousands of tourists will visit Christmas markets this week. Berlin's Christmas markets are open again after remaining closed on Tuesday, and Germany's interior minister urged Germans to visit the markets and "buy an angel."

In a security message, the U.S. Embassy in Berlin told American citizens in the region "to maintain good situational awareness, a low profile and exercise vigilance."

The U.S. State Department said there are no known American victims at this time, but many of the injured in hospitals remain unidentified.

ABC News' Andreas Bechmann and Matt Gutman contributed to this report.