GENEVA — A deadly terrorist attack in central Syria on Saturday threatened to thwart efforts to mold a political solution at peace talks in Geneva, with the U.N. mediator decrying “spoilers” who try to derail efforts to end the country’s disastrous six-year war.

The government’s envoy demanded a firm condemnation from all opposition groups of the synchronized attacks by insurgents on security offices in Homs that left at least 32 people dead, while the opposition retorted that it has long denounced terrorism — even suggesting it may have been an inside job.

“Any party that refuses to condemn these attacks today, we will consider that party to be an accomplice of terrorism,” Syria’s U.N. ambassador, Bashar Ja’afari, told reporters after meeting U.N. envoy Staffan de Mistura in the third day of renewed peace talks — with the sides meeting separately with him so far.

The talks are the first under U.N. mediation in nearly 10 months and build upon a fragile, repeatedly violated cease-fire that was fashioned by Russia and Turkey. Moscow has been a powerful military and political backer of Syrian President Bashar Assad’s government, and Turkey has been a supporter of key rebel groups. The talks also come after Syria’s Russia- and Iran-backed troops regained control of the key northern city of Aleppo in December.

Ja’afari stopped short of suspending the government’s participation outright but said a condemnation of the attacks was a “test” for the fragmented opposition.

An al-Qaida-linked group, known now as the Levant Liberation Committee, claimed responsibility for the twin attacks.

The Syrian government responded with airstrikes against the only neighborhood on the city’s outskirts still under opposition control and other parts of rural Homs.

The government regained control of the city of Homs — one of the first to rise against President Bashar Assad — in 2015. But al-Waer neighborhood remained in rebel hands. Negotiations to evacuate it have repeatedly faltered.

Ja’afari called the attack a bid by states sponsoring terrorism to derail the talks. He singled out Saudi Arabia and Turkey, the two main backers of an array of opposition groups.

Syria’s top opposition delegates said they condemned terrorism but not specifically the Homs attack, all but suggesting it may have been carried out by Assad’s own supporters.

Nasr al-Hariri, head of the main opposition negotiating team, condemned terrorism by the so-called Islamic State group and al-Qaida’s affiliates, but said the Damascus government was the primary “sponsor of terrorism.”

Col. Faleh Hassoun, another member of the delegation, alleged that only people with clearances could access the government’s security office in Homs. He suggested it was aimed to rid the government’s ranks of possible war criminals.

“What really happened today, we can call it liquidation by the regime of those who are wanted for international courts,” he told reporters at a Geneva hotel.

Hassoun also alleged that military intelligence services chief Maj. Gen Hassan Daeboul, who was killed in Saturday’s attack, had been implicated in the assassination of Lebanese Prime Minister Rafik Hariri in Beirut in 2005. Syria’s government is widely believed to have played a role in the killing.

De Mistura, in a statement from his office, said he “strongly condemns the horrific terrorist attack that took place in Homs today,” calling it “an attempt to derail the current intra-Syrian talks in Geneva.

“Spoilers were always expected, and should continue to be expected, to try to influence the proceedings of the talks,” the statement said. “It is in the interest of all parties who are against terrorism and are committed to a political process in Syria not to allow these attempts to succeed.”