The main entrance to the office was sealed off and dozens of police cars and a fire engine rushed to the scene on Wednesday.
There were no immediate reports of casualties.
Reuters released pictures showing police inspecting the car at the gate with the words “Stop Globalization Politics” written in white paint on its right side.
Pictures on social media showed the words “You damn killers of children and old people” written on the other side of the car.
Police did not immediately comment on the incident.
The incident took place as Merkel was scheduled to host a video conference of German state premiers on Wednesday morning in order to discuss an extension to the coronavirus lockdown and further steps to fight the pandemic.
The development comes as Europe is on high alert following a string of terror attacks in the continent in recent months. On October 29, a knife attack, considered a “suspected terror attack,” was carried out at the Basilica of Notre-Dame in Nice, France, killing three people, including a woman.
On November 4, a 20-year-old attacker opened fire on people in Austria’s capital Vienna, killing four citizens. The shooter also injured 22 others in what became the deadliest attack in Austria’s capital for decades, moving through Vienna’s inner city and shooting at passers-by for nine minutes until he was shot dead by police.
Back in December 2016, a 23-year-old Pakistani asylum seeker crashed a truck into a crowded Christmas market in Berlin, killing at least 12 people and wounding dozens of others.
Merkel described that incident as a terrorist attack.