A Russian pilot gets into a Sukhoi Su-25 before taking off at the Hmeimim military base near Latakia, Syria, part of the partial withdrawal of Russian forces. (Vadim Grishankin/AFP/Getty Images)

Syria’s government on Wednesday firmly rejected direct negotiations with opposition envoys, dampening hopes of greater compromise at peace talks after Russia this week began drawing down its troops from the war-torn country.

Meanwhile, signs emerged in Syria that a group affiliated with al-Qaeda may be trying to make gains amid a government-rebel cease-fire and the surprise departure of some Russian warplanes.

Rallies against the militant group, Jabhat al-Nusra, were held in Syria’s northwestern Idlib province after its fighters attacked U.S.-backed rebels, according to residents.

Over the weekend, Jabhat al-Nusra militants killed and detained members of Division 13, a Free Syrian Army rebel group, according to opposition fighters. The rebels’ weapons caches reportedly also were seized.

The moves have raised concerns that Jabhat al-Nusra is exploiting the situation to eliminate potential rivals and seize territory. That, in turn, would further undermine the bargaining power of the opposition delegation taking part in the Geneva talks.

After peaceful demonstrations were met with violence in 2011, protesters took up arms against Syrian government forces. A brutal civil war followed with hundreds of thousands dead and millions displaced. A fragile cease-fire has quieted some of the fighting, for now. (Liz Sly,Jason Aldag/The Washington Post)

“Demonstrations are still happening, and no one can stop things from getting worse,” said a lawyer in Maarat al-Numan, a town in Idlib where the clashes took place. The lawyer spoke on the condition of anonymity because of security concerns.

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The al-Qaeda affiliate is not included in the cease-fire, which was brokered by the United States and Russia and took effect Feb. 27 as part of a political process that helped pave the way for the resumption of peace talks on Monday.

Division 13 received U.S.-made BGM-71 TOW missiles under a covert CIA program in early 2014, although members of the group say that none of the antitank weapons have fallen into the hands of Jabhat al-Nusra militants.

Video of a demonstration in Maarat al-Numan from Monday purports to show Division 13 supporters demonstrating against the extremists. One video claimed to show protesters setting fire to a building used by Jabhat al-Nusra, possibly in an attempt to secure the release of detained rebels.

“There are still 17 officers and members from Division 13” detained by Jabhat al-Nusra and allied extremists, the rebel group’s commander, Col. Ahmed Saud, wrote on Twitter on Wednesday.

In Geneva, the talks have struggled to gain momentum.

The Washington Post traveled to Damascus, Syria, during a "cessation of hostilities," which has brought a stop to some of the fighting inside the city. (Loveday Morris,Jason Aldag/and Lorenzo Tugnoli for The Washington Post)

The Syrian government’s lead representative, Bashar Jaafari, dismissed the opposition delegates as “terrorists” who should apologize for Syria’s civil war.

He also questioned the legitimacy of the opposition team, represented by an umbrella group known as the High Negotiations Committee, suggesting that it did not adequately reflect the full spectrum of groups fighting Syrian President Bashar al-Assad.

“No Syrian faction can monopolize the representation of all the opposition,” Jaafari told journalists after meeting the U.N. envoy to Syria, Staffan de Mistura.

The HNC, which has the backing of dozens of rebel groups, rejects such claims as an attempt by the government to stymie the talks.

[Russian withdrawal resonates from war zones to peace talk]

The talks involve de Mistura shuttling between the opposing sides, but the goal remains direct political dialogue between the government and the opposition groups.

Diplomats and opposition members have expressed guarded optimism about the Geneva effort, citing as a positive step Russian President Vladimir Putin’s announcement Monday to withdraw most of his military forces from Syria.

Many hope the move is an attempt to pressure Assad to make concessions in the talks, which were restarted after a round last month collapsed because of intense fighting in Syria.

“Mr. Jaafari still is of the delusion that he can try to filibuster the opposition to leave town, but it’s not going to happen this time,” said a Western diplomat in Geneva, who spoke on the condition of anonymity because of a lack of authorization to discuss the issue publicly.

Jaafari also repeated the government’s denial that Putin’s announcement took the Syrian leadership by surprise. Russia began its military intervention in the Syrian conflict in September, firing airstrikes at rebel groups in attacks that have bolstered Assad’s rule and weakened the armed opposition.

“It wasn’t a surprise for us. It was coordinated,” said Jaafari, who also is the Syrian ambassador to the United Nations.

Meanwhile, on Wednesday, a powerful Kurdish party in Syria proposed a plan under which the country’s largely Kurdish north would become its own region. The proposal, however, met with opposition from many, including diplomats in Geneva and the Syrian opposition delegation. They said that no formal discussions about federalism have been held and that the Kurds made the announcement unilaterally.

On Tuesday, the opposition expressed concern to de Mistura during an hour-long meeting about a lack of promised humanitarian aid to besieged Syrians and the government’s failure to release detainees held in its prisons.

Bassma Kodmani, an HNC negotiator present at the meeting, later cited “no results at all on that issue.”

U.N. resolutions and various international agreements call for the release of thousands of people thought to be arbitrarily detained by the government.

Zakaria Zakaria in Istanbul contributed to this report.

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