Google’s planned acquisition of an online advertising business in Russia was blocked by the country’s antitrust authorities on Thursday, dealing a setback to the search company’s efforts to raise its profile in one of the few big countries where it does not already have a dominant position.

The US company had agreed to pay $140m for Begun, a contextual advertising business owned by Russian internet portal Rambler, as it tried to catch up with Yandex, the country’s leading search company.