Twin explosions on Monday hit the regional headquarters of Turkey's main pro-Kurdish party in two cities, amid escalating tensions in the run up to June 7 legislative elections, a party official said.

Six people were injured in the blast at the office of the People's Democratic Party (HDP) in the southern city of Adana, three of them seriously, the official told AFP.

The official said the facade of the building sustained damage.

Another blast occurred in nearby Mersin in southern Turkey when a bouquet of flowers sent to the party office exploded, the party official said. Video footage showed several people with bloodied faces.

The motives and causes of the blasts were not immediately clear. The HDP's co-chairman Selahattin Demirtas was due to address a rally in Mersin later in the day.

The government immediately condemned the attack, with Culture and Tourism Minister Omer Celik saying on Twitter it took an aim at at "the HDP, all political parties and Turkey's election process."

Finance Minister Mehmet Simsek said in live comments broadcast by NTV television: "This is a political struggle which should never be contaminated by violence."

In April, unidentified assailants opened fire on the HDP headquarters in the capital Ankara, with no casualties. The government condemned that attack as a blow to Turkey's democracy and stability.

Tensions are mounting ahead of Turkey's key elections next month in which the HDP is seeking to clear the 10 percent quota to take seats in the parliament.

The HDP's success could dent the ruling AKP party's plans to reach a thumping majority in the 550-seat parliament in order to change the constitution and create a presidential system.

Deputy Prime Minister Yalcin Akdogan has said this month it would be "super" if the pro-Kurdish HDP failed to clear the 10 percent threshold.

Dengir Mir Mehmet Firat, a former AKP politician and currently the HDP's candidate for Mersin, put the blame on the government for the latest blasts.

"The prospect of the HDP clearing the threshold on the horizon scares some (people). The government which rules the state must be behind all this," he said in comments published in Turkish media.

"We will not succumb to provocation," he added.

President Recep Tayyip Erdogan, who steered Turkey as prime minister for 11 years, has appealed to his supporters to help elect 400 AKP lawmakers in June's vote, giving him the backing to rewrite the constitution -- and assume full executive powers himself.