And Turkish President Recep Tayyip Erdogan berated the new US administration for failing to immediately accept its version of the incident.

The mass arrests were announced a day after Ankara said Kurdistan Workers' Party (PKK) rebels had executed the 13 captives. The PKK blamed Turkish airstrikes on their bases for their deaths.

Most of the captives were soldiers and police abducted in southeast Turkey and kept in an Iraqi cave.

The PKK has been waging an insurgency against the Turkish state since 1984 thought to have left tens of thousands dead.

The Turkish interior ministry did not give details on where the raids took place but said heads of the pro-Kurdish Peoples' Democratic Party (HDP) in cities and districts were among those captured.

The HDP is Turkey's second-largest opposition party. It denies all formal links to the PKK -- a group classified as a terrorist organization by United States and Ankara's other Western allies.

But Washington has supported another Kurdish militia in Syria that Turkey considers as an offshoot of the PKK.

The killings of the 13 men has inflamed Ankara's strategic but volatile relations with Washington, AFP reported.

The US State Department said Sunday it "deplores the death of Turkish citizens" but was waiting for further confirmation that Ankara's account of what happened was true.

Erdogan branded Washington's response "a farce".

"You said you did not support terrorists, when in fact you are on their side and behind them," he said in televised remarks.

Turkey this month launched a military operation against PKK bases in northern Iraq that Erdogan said on Monday was designed in part to free the 13 hostages.

The PKK said the 13 men had died when Turkish forces bombed the cave where the men were being kept after being abducted in raids that began in 2015-6.

"If reports of the death of Turkish civilians at the hands of the PKK, a designated terrorist organization, are confirmed, we condemn this action in the strongest possible terms," the State Department said in a statement.

Turkey said 12 of the men had been executed with a single shot to the head while the thirteenth was shot in the chest.

The incident threatens to escalate tensions across Iraq and Syria while delivering an early test to Erdogan's relations with the new US administration of President Joe Biden.

Reporter's code: 50101