Turkish President Recep Tayyip Erdogan has said there will be no change to the secularism of the Turkish state, following a row provoked by calls by the speaker of the parliament for the introduction of an Islamic constitution.

"My views are known on this," Erdogan said in televised comments during a visit to the Croatian capital Zagreb on Tuesday. "The reality is that the state should have an equal distance from all religious faiths."

"This is laicism," he explained, using the French term referring to the constitutional separation of religion and the state.

Controversy erupted on Monday after parliamentary speaker Ismail Kahraman, a member of Erdogan's ruling Justice and Development Party (AKP) said that Turkey "must have a religious constitution".

"Why should we be in a situation where we are in retreat from religion?" he said.

The comments have heightened concerns among Turkish secularists about AKP plans to change the current constitution, which was introduced following a military coup in 1980.

The AKP, which has governed Turkey since 2002, describes itself as socially conservative but the party has its roots in political Islam.

The leader of Turkey's main opposition Republican People's Party (CHP), Kemal Kilicdaroglu, said a secular constitution was essential to guarantee freedom of religion. "Secularism is a guarantor of all faiths. It means freedom of religion and conscience. Look at the Middle East. You still haven't learnt the lesson," he said in comments addressed to Kahraman. "Secularism also means religion not being exploited politically," he said. But the head of parliament's constitution commission, AKP member Mustafa Sentop, said no discussions were under way to remove secularism from the constitution.

The speaker was "not speaking on behalf of his party", he said. Several rounds of negotiations between the AKP and political rivals on proposed changes to the constitution have so far failed - most recently in February - with the opposition rejecting the increasingly powerful role of the presidency under Erdogan.

On Wednesday Prime Minister Ahmet Davutoglu pledged that Turkey's draft constitution would guarantee secularism.

"Secularism will feature in the new constitution we draft as a principle that guarantees citizens' freedom of religion and faith and that ensures the state is an equal distance from all faith groups," Davutoglu said in a televised speech.

Secularism has been embedded in the Turkish constitution since 1928, following reforms by the republic's founder, Mustafa Kemal Ataturk.

Prior to the rise of the AKP, the military would often intervene if political parties managed to take power - or come close to taking power - that threatened to undermine the country's secularism.