But after two of them were chased and arrested, the third returned to the bank and held people hostage, a police spokesman said.
He tried to escape using four hostages as human shields and threatening to set off two grenades, but eventually returned inside the building, media reports
Dozens of police had surrounded the bank and a helicopter hovered above the area, which was cordoned off.
The gunman had earlier fired shots in the air, police said, but added that no one had been wounded.
According to preliminary information, 14 people were initially held hostage.