Comments made by Russian Foreign Minister Sergey Lavrov are at the verge of being "ill-mannered", his Bulgarian counterpart Daniel Mitov has said.

Mitov's words referred to the remarks made by Lavrov earlier this week, after Bulgarian Prime Minister Boyko Borisov told US business representatives that Sofia needed more support and cooperation after having denied overflight to a number of Russian aircraft and suspended key Russian projects.

That prompted Lavrov to say Borisov must feel ashamed before voters of his statement.

But in Mitov's words, the theory Bulgaria is renouncing projects to the benefit of another country is "manipulative".

Instead, "when a project is not beneficial to a country, is not made in compliance with the rules, there is nothing dramatic about stopping it."

"I am not ashamed," he told bTV station.

He also downplayed Bulgarian moves not to allow overflight to Syria-bound Russian planes, the last one being on Friday.

Sofia then explained that Moscow had not informed of its overflight request five days in advance.

"Russians have alternative routes and have already transported what they want," Mitov noted, added the issue of Russian planes had already become "boring" for people.

Asked about Thursday's incident with the death of a migrant near the Bulgaria-Turkey border, Bulgaria's top diplomat asserted that Bulgaria would "defend its reputation" whatever international reactions are.

"We have never denied [asylum] to anyone fleeing wars, but this should happen in accordance with the respective procedures."

"We have our responsibilities and we are delivering on them," Mitov added, referring to Bulgaria's commitment to protection of the EU external borders.