ANKARA, Turkey — Turkish President Recep Tayyip Erdogan laid into the United States, accusing it of supporting Kurdish militants on Monday, days after Turkish troops found the bodies of 13 Turkish soldiers, police and civilians abducted by Kurdish insurgents in a cave complex in northern Iraq.

Addressing his ruling party's supporters in the Black Sea city of Rize, Erdogan also took aim at a U.S. State Department statement which deplored the deaths of the hostages, but added that the United States would condemn the deaths "in the strongest possible terms" if it is confirmed that they died at the hands of the Kurdistan Workers' Party, or PKK.

"Did you not say you don't support the PKK, the YPG or the PYD? You are with them and behind them pure and simple," Erdogan said, referring to Syrian Kurdish groups linked to the PKK, which Turkey considers to be terrorists but which were allied with the United States in the fight against the Islamic State. 

"If we are together in NATO, and if we are to continue our (alliance) in NATO, you have to be sincere toward us," Erdogan said. "You must not take the side of the terrorists. You have to be on our side."

Foreign Minister Mevlut Cavusoglu expressed Turkey's "unease" over recent U.S. statements during a telephone call with U.S. Secretary of State Antony Blinken, the ministry said.

In their first conversation since U.S. President Joe Biden's administration took office last month, the two also discussed a series of other disagreements between the NATO allies and agreed to "develop an open and sincere dialogue based on mutual respect," the ministry said in a statement.

Earlier on Monday, Turkey summoned U.S. Ambassador David Satterfield to the Foreign Ministry and conveyed Ankara's reaction to the U.S. statement "in the strongest way possible," ministry spokesman Hami Aksoy said. 

The victims were discovered in a cave complex in the Gara region, near the Turkish border, during an operation against the PKK, launched on Feb. 10, that had aimed to free the hostages. 

Twelve of the victims were shot in the head and one died of a shoulder bullet wound, the country's defense minister said Sunday. The 13 were kidnapped inside Turkey in the last five or six years.

Erdogan said 51 PKK militants were killed during the offensive and vowed to press ahead with cross-border offensives against the PKK in Iraq, and against the Syria-based militants.

"Neither Qandil, nor Sinjar, nor Syria — as of now no place where the terrorists are located is safe for them," Erdogan said, in reference to areas in northern Iraq where the PKK maintains bases. "We have the power, capability and determination to come down hard on the terrorists everywhere."

Turkish authorities meanwhile, detained more than 700 people with alleged links to the PKK, including local leaders of the main pro-Kurdish political party — the third largest party in Turkey's parliament, the Interior Ministry announced. The suspects were detained in operations in 40 provinces, following the execution of the hostages. 

Erdogan's government, which accuses the Peoples' Democratic Party, or HDP, of having links to the PKK, has been cracking down on the movement over the past five years, by sacking elected mayors from office and jailing thousands of members, including its former chairman, Selahattin Demirtas.

In a statement carried by the PKK-linked Firat news agency, the PKK said "prisoners of war" consisting of members of the Turkish security forces and intelligence agency were killed as a result of Turkish air strikes.

Three Turkish troops also died during the operation to free the hostages and three others were wounded, the defense ministry has said. 

Tens of thousands of people have been killed since the PKK, which is designated a terrorist organization by the U.S. and the European Union, began an insurgency in Turkey's majority Kurdish southeast region in 1984.