Police tweeted that the incident appeared to be an attempted robbery and that several shots were fired in a shop in the German capital. They added that the situation was under control. In a later tweet police said that reports of shots were unconfirmed and they were continuing to investigate.
Pictures and videos show officers at the scene with the area cordoned off.
There were no injuries, according to reports.
A witness said they heard gunshots before people shouted and fled the cafe, Frankfurter Rundschau reported.
Another witness told Morgen Post he was about to get a coffee when he heard several bangs.
A Police spokesman said: “During lunch time there was the suspicion that there had been a robbery at a branch of the chain Starbucks, a café of the Starbucks chain.
“We have witness testimony that a perpetrator allegedly fired shots. We cannot confirm the shooting at this moment. Witness statements say that no gun has been spotted but that there were only loud bangs that could be attributed to this person who could have come into consideration of being the suspect.
“We have a vague description of the suspect which we are looking into. Special forces are currently thoroughly searching a building at the moment, in which we suspect the possible perpetrator.
“At the moment we are not able to determine a person or a suspect, at this moment we have also not been able to find a gun. The shots fired have so far also not been confirmed, therefore we continue to investigate. We continue to suspect a crime happened, which we are investigating. There is a possibility that the gun control law has been breached.”
Checkpoint Charlie is located on the corner of Friedrichstraße and Zimmerstraße.
It was the best-known border crossing between East and West Germany during the Cold War.
(Additional reporting by Katie Harris)