Turkey's justice ministry and the offices of its ruling AK Party were attacked with homemade bombs and a flame thrower in the capital Ankara on Tuesday, days ahead of an expected ceasefire with Kurdish militants.
The attack shattered windows on the seventh floor of the AK Party building, where Prime Minister Tayyip Erdogan has an office, according to a Reuters cameraman, while two devices also exploded outside the justice ministry several miles away.
Erdogan, who left Ankara earlier on Tuesday for an official visit to Denmark, had been briefed on the attacks, Interior Minister Muammer Guler told a hastily assembled news conference.
"We cannot say who was behind these explosions for sure but we have some rough ideas ... they are enemies of democracy and their main target is democracy," he said.
There was no immediate claim of responsibility. Kurdish militants, far-left groups, ultra-nationalists and Islamic radicals have all carried out attacks in Turkey in the past.
The most recent bombing was by a member of the Revolutionary People's Liberation Party-Front (DHKP-C) leftist group who blew himself up at an entrance of the U.S. embassy on Feb. 1, killing a Turkish guard.
Twelve people were detained in Istanbul early on Tuesday in an operation against the DHKP-C, listed by Turkey and the United States as a terrorist organisation. The group has carried out attacks in the past in retaliation for arrests of its members.
Asked if the DHKP-C may have been responsible for Tuesday's blasts, Guler said: "Nothing is clear yet. We have some conjectures and will act when proven."
Kurdish peace plan
Tuesday's explosions occurred two days ahead of an expected ceasefire call by jailed Kurdish rebel leader Abdullah Ocalan, who has been in talks with state officials to try to end a three-decade conflict that has killed some 40,000 people.
The ceasefire call, expected to coincide with the Kurdish New Year on Thursday, would be a major step in what is shaping up to be the most serious bid yet to end Turkey's conflict with the Kurdistan Workers Party (PKK) militants.
AK Party spokesman Huseyn Celik said the attacks would not derail the peace process.
"Our decisiveness will continue ... such turbulence cannot push us from our path," he told the news conference.
The conflict with the PKK, considered a terrorist group by the United States and the European Union as well as Ankara, burns at Turkey's heart and there are forces on both sides that stand opposed to a resolution.
Intelligence officers and Kurdish politicians have been speaking to PKK leader Ocalan since October, holding talks on his island prison off Istanbul where he has been held since 1999 in a effort to hammer out a peace deal.
Ocalan is reviled by most Turks, many of whom hold him personally responsible for the conflict's high death toll, and the contacts have risked enraging Turkey's conservative establishment and nationalists.
In a statement conveyed from his cell via a Kurdish politician, Ocalan said he would make a "historic" appeal on Thursday, raising expectations of a ceasefire.
Such truces have been agreed and failed before in the war.
The PKK originally demanded full independence for a Kurdish state in southeastern Turkey, but has moderated its goals to broader political and cultural autonomy.
Erdogan has made a number of concessions on cultural and language rights as part of his efforts to forge a settlement.