Bulgarian Prime Minister Boyko Borisov has expressed his disappointment with Tuesday's ruling of the Macedonian Supreme Court that deprived a Bulgarian mother of custody over her small daughter.

The Supreme Court overturned last years' ruling of the Court of Appeals that returned little Suzanna to the custody of her mother, Bulgarian Spaska Mitrova.

"I believed the Spaska Mitrova case is over," Borisov told reporters, reminding that the Macedonian court had ruled in her favor at several instances.

"The entire Bulgarian community has supported her," he added.

"As a country, we could hardly comment the court and its ruling. It is highly unpleasant for me to comment on a topic like this," the Bulgarian PM noted, saying the case is a "test in diplomacy."

"I will not link this case to our attitude towards Macedonia in the European Council, but I declare that Bulgaria will be very strict when the criteria are adopted for (Macedonia's) accession to the European community. Extremely strict," Borisov stated.

The Bulgarian Prime Minister pointed out that his country has seen its relations with Serbia and Kosovo significantly improved.

"I sincerely hoped our colleagues from Macedonia would do the same, but hardly a day or a week passes without us receiving signals that the Bulgarian nation does not deserve at all," he said.

In 2011, Supreme Court of Appeals in Macedonia's Skopje granted custody rights to Spaska Mitrova, who was thrown for three months in jail in 2009 for preventing her former husband from meeting their child.

The infant was taken away from the mother by force, following a series of contradictory court decisions.

The young woman holds a Bulgarian passport and perceives herself as Bulgarian. She was sentenced and served time in a Macedonian prison over charges she did not allow her husband to see Suzanna. She was released on parole, but then the parental rights case began.

Mitrova has been the cause of diplomatic scandal between the two countries since 2009.

In the aftermath of the news about the Court's rule in March 2009, the Bulgarian Foreign Affairs Ministry expressed deep concern over the way the custody trial was held, defining it as non-transparent and staged in the conditions of a very negative public environment, which included physical force, detention, and depriving the mother of her right to see her child.