Istanbul - Twin bomb attacks on the offices of Turkey's pro-Kurdish People's Democratic Party (HDP) were carried out by a militant linked to an ultra-leftist group, Turkish Prime Minister Ahmet Davutoglu said on Thursday.
Davutoglu said a suspect had been identified as having links to the Revolutionary People's Liberation Party-Front (DHKP-C), although no one has been arrested over the attacks on Monday on HDP's regional headquarters in the southern cities of Adana and Mersin.
"This assailant had been previously arrested in recent years for being a member of the terrorist group DHKP-C," Davutoglu told a rally in the Black Sea city of Sinop.
The suspect is still at large.
In April two DHKP-C militants took a prosecutor hostage at an Istanbul courthouse and held him for hours before all three were killed in a shootout with the police.
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Six people were injured in the blast at HDP's Adana office caused by a suspect parcel while a bouquet of flowers sent to the party's office in the nearby city of Mersin also exploded.
In a separate statement, the interior ministry said both attacks had been carried out by a man, who had been arrested in 2007 in Ankara for links to the DHKP-C.
The assailant placed the bombs on the HDP's offices in Adana and Mersin a day before the attack, the statement said.
"Meticulous efforts" were under way to locate and detain the man, it said.
The attacks were the latest in a string of violence against HDP targets in the run-up to the increasingly tense legislative elections on June 7.
The HDP is seeking in the election to break the steep 10 percent threshold needed to take seats in parliament.
Its 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 make the president, instead of the prime minister, Turkey's most powerful figure.
Davutoglu also claimed that the DHKP-C and the separatist Kurdistan Workers' Party (PKK) - which has waged an armed insurgency in the southeast for Kurdish autonomy - had cooperated for the attacks, saying the two were linked.
"Do you see the game being played out? All masks are falling one by one," he said.
Both the DHKP-C and the PKK are considered a terrorist group by Turkey, the European Union and the United States.