Ukraine has raised the alarm over an increase in Russian forces near its eastern border as violence has risen along the line of contact separating its troops from Russia-backed separatists in its Donbass region.
"The Chancellor demanded that this build-up be unwound in order to de-escalate the situation," Germany's government said in a readout of a telephone call between Merkel and Putin.
There were no immediate reports of casualties and it was not clear if Merkel was inside the building. Dozens of police and a fire engine attended the incident. The driver, who appeared to be in late middle age, was taken away in a wheelchair.