Türkiye criticized the European Parliament (EP) for authorizing terrorist PKK supporters to display propaganda during the plenary session on Wednesday.
In a statement, the Foreign Ministry said it was unacceptable for the terrorist group and its affiliates to easily enter EP premises and demonstrate.
It further said the incident "reveals the inability and insincerity of the European Union and, in particular, the EP in the fight against terrorism."
The ministry noted that EP and EU's indifference to the PKK, despite the fact that it is recognized as a terrorist group by the bloc, will make it impossible to end the terrorist group's presence in the EU and that it is necessary to investigate how the PKK members entered the EP premises.
The debate session was halted for three hours and MEPs left the chamber as the terrorists brandished banners bearing terrorist Abdullah Öcalan's image and shouted slogans hostile to President Recep Tayyip Erdoğan.
The French centrist MEP Bernard Guetta said the protesters were on an upper deck above the Strasbourg chamber, some sitting on a balustrade and dangling their legs above the parliament's floor.
Another MEP, German social democrat Bernd Lange, said the way the protesters were clinging precariously to the balustrade appeared as if they were threatening to jump.
Parliamentary security intervened to talk the group down and no one was hurt. Later parliamentary speaker Roberta Metsola reopened the debate and said the protesters had left.
PKK supporters have been known to hold demonstrations in front of the Council of Europe and EU institutions.
The PKK is listed as a terrorist organization by Turkey, the EU and the U.S. and is responsible for the deaths of 40,000 people, including women, children, and infants. The YPG, which also has a presence in Europe, openly sanctioned by several governments, is the PKK's Syrian branch.