A man has been arrested at gunpoint by officers near the MCG after driving erratically then ramming a police vehicle in a chase on Tuesday afternoon.

Officers swarmed on the man just after 4pm following reports he was seen driving erratically in a black sedan near the intersection of Wellington Parade and Powlett Street in the CBD, Victoria Police said.

Witness Alexander Hipwell estimated at least 15 police vehicles swarmed the scene, including critical incident response units.

Mr Hipwell was sitting inside the Laurent Boulangerie Patisserie at Wellington Parade-Powlett Street intersection when he saw heavily armed officers drag a Caucasian man from a stationary black Toyota Aurion.