"The Bulgarian foreign ministry has refused flights over Bulgaria of Russian military transport planes en route to Syria," the spokeswoman told Reuters, adding that the decision was taken in the past few days.
Russia will deliver the humanitarian supplies to Syria through Iran, the newspaper said.
Bulgarian Defense Ministry spokesman Daniel Stefanov confirmed that the country had closed its airspace to Russian aircraft delivering humanitarian aid to Syria.
"Yes, we can confirm that Bulgaria has denied its airspace to Russian aid flights to Syria," Stefanov told Sputnik.
"The reason for the refusal is associated with incorrect information in the requests to fly over the territory of the Republic of Bulgaria regarding the purpose of the flights and the cargo," the statement said.
On Saturday, the US embassy appealed to Athens with a request to prohibit the flights of Russian aircraft providing aid to Syria, however, Greece refused to do so, a source told RIA Novosti.
First Deputy Head of the International Committee of the Russian Federation Council Vladimir Jabbarov said Monday that Russia may use new flight aid routes to Syria if Greece closes its airspace to Russian aircraft.
The Russian senator stressed that Iran, Turkey and Central Asian states may assist Russia with regard to its humanitarian mission in Syria.