"The planes were said to carry humanitarian aid but we had information -- that we had every reason to trust -- that the declared cargo was not the real one," foreign ministry spokeswoman Betina Zhoteva told AFP.
Zhoteva said the decision was taken late last week but did not give details about how many planes were concerned.
She said the decision was taken independently without pressure from NATO partners.
A Russian official refused to believe Bulgaria's decision was made without pressure from the US.
"The fact that the Bulgarians are the first to respond (to the request from Washington) -- they will have that on their conscience," said Vladimir Djabarov, vice-president of the Russian foreign affairs council.
He told state press agency TASS that Russia was only supplying "humanitarian cargo" to Syria, adding that it is "not profitable to transport weapons by plane".
Washington is concerned that Moscow could be increasing its military support to Assad, an issue raised by US Secretary of State John Kerry with Russian counterpart Sergei Lavrov at the weekend.
Russia had asked Greece to allow the passage of two planes between September 1 and 24. A Greek foreign ministry official told AFP they were examining the request and had yet to take a decision.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
