At least four police officers have been killed and two others wounded in a roadside bomb explosion in Kurdish-majority southeastern Turkey, according to the local governor's office.

The blast on Monday occurred in the Sur neighbourhood of Diyarbakir province, where the Turkish army launched an intensive campaign last year against the outlawed Kurdistan Workers' Party (PKK).

"An attack was carried out when explosives ... detonated as an armoured vehicle carrying our riot police was passing by," the governor's office said in a statement.

The toll of four police killed raised a previous figure of three dead.

READ MORE: Turkey's war on the PKK

The state-run Anadolu news agency said the wounded were being treated in Dicle University's Medical Faculty Hospital, which is located close to the site of the blast.

There was no immediate claim of responsibility.

The governor's office called it "an atrocious terror attack", pledging that Turkey would continue to fight "against terror" with determination.

Turkey has been hit by a series of bombings over the past few years, including five in Istanbul.

Dozens of attacks blamed on the PKK and the Islamic State of Iraq and the Levant (ISIL) groups took hundreds of lives.