Russian authorities have halted Google's purchase of an online ad service, the Associated Press reported.

Google announced in July it would spend US$140 million to buy the ad service, ZAO Begun, from Rambler Media Ltd., which owns one of the most popular online portals in Russia. The deal was expected to be finalised during the third quarter.

Google said it was part of its plans to improve service for users, partners and advertisers in Russia, one of the fast-growing digital advertising market, AP reported in an article posted by Yahoo Tech.

However, Google said in a statement Thursday it “was very disappointed that Russia's Federal Anti-Monopoly Service, or FAS, decided to block the deal.” Rambler also announced in an online notice that the deal was rejected, according to the AP.

“At this time we are reviewing FAS's decision. Once this process is complete, we will decide on our next steps,” said Google.

The Federal Anti-Monopoly Service did not elaborate on the reason for the rejection in its brief statement, the AP reported.