Bulgaria’s ban on Syria-bound overflights of Russian aircraft carrying humanitarian aid will lead to an increase in the number of refugees from the war-torn country, Moscow said on Thursday.

“As far as the Bulgarian ban is concerned, the cargo was humanitarian aid for the Syrian people,” Russian Foreign Ministry spokeswoman Maria Zaharova said, according to TASS.

Zaharova also said that Bulgaria’s motives for the ban were “incomprehensible” and had caused “profound bewilderment.”

To justify the ban, Bulgaria claimed the Russian planes allegedly carried weapons for Syrian government forces, she added.

Moscow “would like to draw Bulgaria’s attention to the moral and political responsibility for the consequences of their action”, which worsens the already grave humanitarian crisis in Syria and leads to increased flow of migrants.

Moscow has already said it would use alternative routes to deliver humanitarian assistance to Syria after Bulgaria closed its airspace for Russian planes with such cargo.

Asked by reporters on Wednesday whether Russia would agree that its cargo planes overflying Bulgaria's territory en route to Syria were inspected by the Bulgarian authorities, the Kremlin spokesman Dmitry Peskov replied: "The Russian Foreign Ministry has already noted that there are alternative routes for delivering humanitarian aid that will be used," according to TASS.

The press secretary of the Russian Embassy in Tehran Maxim Suslov said on Wednesday that Iran had agreed to open its airspace for Russian planes carrying humanitarian cargo to Syria.