Turkish President Recep Tayyip Erdogan on Monday urged the European Union and other Western nations to step up support for Ankara's fight against Kurdish militants, as he addressed a meeting of NATO lawmakers.

Erdogan said he expected the backing of NATO countries in Turkey's fight against "all terror groups" including the Kurdistan Workers Party (PKK), Islamic State (IS) jihadists and the group blamed by Ankara for the failed July 15 coup.

He called on the European Union to tighten its approach to the PKK, which Brussels designates as a terror group but whose members, according to Erdogan, are allowed to roam freely within the bloc.

"Those who have a hesitant attitude against terrorist organisations will be hit themselves sooner or later," he said in a speech to deputies at the NATO Parliamentary Assembly.

Turkey has been a member of NATO since 1952 but its bid to join the European Union has been further set back by disputes over the extent of its crackdown in the wake of the coup.

Erdogan had at the weekend mooted that Turkey could join the Shanghai Cooperation Organisation (SCO), a loose security and economic bloc led by Russia and China sometimes seen as an eastern counterpart to NATO.

But he did not refer to this in his speech in Istanbul to the NATO meeting.

NATO Secretary General Jens Stoltenberg meanwhile emphasised the alliance's "solidarity" with Turkey in the wake of the coup and said Ankara "has the right" to prosecute those responsible.

Pressed by a Dutch lawmaker to condemn the crackdown that has seen over 35,000 arrested, Stoltenberg said he had told Turkish leaders all measures had to be taken within the rule of law.

He said he welcomed cooperation between Turkey and the Council of Europe over the legal measures after the coup, saying this should be an "important tool" to ensure the rule of law and human rights are applied.

He added he wanted to see "more assurance measures" from NATO states to help Turkey on its unstable borders, in addition to the current surveillance flights and deployment of missile batteries on the Syrian frontier.

Stoltenberg said last week Turkish officers serving in NATO command posts had asked for asylum following the failed putsch.

Later Monday in a statement Stoltenberg said he had spoken with the Turkish president about the filling of Turkish posts in the alliance's command structure, which he described "as a national decision for Turkey - as it is for any other NATO ally".

He added that "NATO's commitment to the security of Turkey is absolute."