“We express our sincere condolences to the relatives of the victims and the Turkish people and wish a speedy recovery to the injured,” the Russian diplomatic mission said in a statement.
The explosion occurred during the day on the pedestrian street Istiklal.
The Prosecutor General's Office of the city opened a criminal case, the version of the attack is being considered.
According to the latest reports, six people died.
There are no Russians among the victims.
In total, 81 injured citizens were reported, two people are in serious condition.
Turkish President Recep Tayyip Erdogan stressed that the explosion in Istanbul "smells like a terrorist attack."