Recep Tayyip Erdogan was speaking at the 62nd session of NATO’s Parliamentary Assembly in Istanbul on Monday.

Erdogan said Turkey, as a victim of terrorism, could not tolerate how groups like the PKK -- an illegal organization in the EU -- could be “comfortable” in European countries.

Belgium in particular has been criticized by Turkey, which has accused it of failing to act against the PKK.

In August, the group`s supporters in Brussels were allowed to celebrate the anniversary of the terror organization`s first attack. Five months earlier, PKK sympathizers set up tents outside EU buildings ahead of a Turkey-EU summit.

Aside from Belgium, the PKK is also active in other EU countries such as Germany, Austria, Denmark, France, the Netherlands, Sweden and Greece.

Erdogan went on to advise “our friends” to take steps against illegal groups at home lest their presence in those respective countries come back to haunt them.

Erdogan also criticized some states for their military support of PKK affiliates in Syria and Iraq, such as the PYD and its military wing, the YPG.

The Turkish president said such groups had weapons from abroad and Turkey even knew the serial numbers of such armaments:

“And we have all of these weapons, even their serial numbers. We know them ... Some say: ‘These are weapons given in the old days.’ Others say: ‘We do not accept the PYD and YPG as terrorist organizations.’”

Erdogan said some countries did not accept the PYD and YPG as terrorists because they were fighting Daesh:

"Al-Nusra is fighting against Daesh as well. Can you say that a terrorist is good because it is fighting against another terrorist?"

Turkey has been critical of American air support and arms supplies to the PKK/PYD because it has been designated a terrorist organization by the U.S., Turkey and the EU.

However, the President Barack Obama administration has cited the fight against Daesh as justification of its support for the PKK-linked group in Syria.

The PKK resumed its decades-old armed campaign in July last year and has been responsible for the deaths of more than 1,100 members of the Turkish security forces and civilians, including women and children. The PKK and its Syrian offshoot the PYD are listed as terror groups by Turkey, although the U.S. and EU only view the PKK as a terrorist organization.

Ankara needs strong support in the fight against terrorism, Erdogan told the NATO audience.

"Turkey is a barrier between the terror organizations and the rest of the world, especially Europe. If we fail in this fight, if this barrier falls, terrorists will cover the world with fire and blood," he added.

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