Prime Minister Binali Yıldırım has told his Spanish counterpart, Mariano Rajoy, Turkey supports Spain's territorial integrity.
According to a prime ministry source, Yıldırım in a phone call stressed Turkey's support for the political unity of "ally and friend" Spain.
Yıldırım also said he believed the Catalonia issue would be resolved in accordance with the Spanish constitution, the source, who spoke on condition of anonymity due to restrictions on talking to media, said.
The two leaders also agreed on strengthening joint effort to improve relations between the two countries.
Catalonia's separatist-led parliament voted to declare independence from Spain last Friday.
Minutes later the Spanish Senate enacted Article 155 of the constitution, which allows Madrid to take direct control of Catalonia, dismiss separatist leaders and trigger regional elections.
The Turkish Foreign Ministry said the Catalan move was "not a step in the right direction".
"Respect for the territorial integrity and the constitution of Spain as well as the will of the Spanish people are fundamental. The unilateral decision of the [Catalan] parliament does not comply with the constitution and the laws of Spain and does not reflect the will of Spain as well as the people of this region," it said in a written statement.
"We hope that the regional government of Catalonia will not insist on this unilateral decision, which has no constitutional legitimacy and could lead to tension and escalation. We believe that this issue will be resolved based on democracy and the rule of law," it added.
"Turkey has no doubt that Spain, with whom Turkey has bonds of friendship and alliance, will overcome this challenge. Turkey supports Spain's efforts in this aspect."
