BEIRUT (AP) — Syrian opposition fighters launched a new offensive against government forces on Monday in a number of areas in the country's northwest, further straining a fragile cease-fire as peace talks resume in Geneva.

Around 10 rebels groups, including some represented at the talks, said in a statement that the attacks in rural parts of the Latakia province, a government stronghold, are in retaliation for violations of a U.S. and Russian-brokered cease-fire that took effect in late February.

The offensive, called "The Battle to Redress Injustices," is in response to government attacks against refugee camps and residential areas, the statement said. Different factions shared videos of their fighters lobbing rockets at government positions in the Jabal al-Akrad area, close to the rebel-held northwestern province of Idlib. In social media postings, the groups claim to have gained ground.

The Britain-based Syrian Observatory for Human Rights confirmed the rebels seized control of at least two areas and said al-Qaida's branch in Syria, the Nusra Front, is taking part in the fighting. Neither the Nusra Front nor the Islamic State group is included in the cease-fire.

The cease-fire had reduced violence across Syria despite alleged violations on both sides. The opposition says the government has breached the agreement more than 2,000 times. The cease-fire was intended to facilitate talks in Geneva, which resumed last week.

The truce has held in most of Syria, except in the north, where it has practically collapsed. The Nusra Front is deeply rooted in the areas in northern Syria controlled by opposition forces, complicating the oversight of the truce.

Insurgents meanwhile attacked government positions in the rural part of the Hama province, adjacent to Latakia, activists said. The Observatory said government helicopters dropped barrel bombs on the village of Khirbet Naqous after fighters seized it earlier in the day.

A Syrian opposition member in Geneva, Mohammed al-Abboud, said the rebels have the right to defend themselves.

"We have the right to retaliate and defend ourselves in case we are attacked and we will not be silent about any aggression and we will continue our main mission to defend civilians," al-Abboud said in comments published on the Syrian opposition High Negotiation Committee's Twitter account.

Syria's U.N. ambassador Bashar Ja'afari, who is leading the government's delegation in Geneva, accused rebel fighters of calling for a "revocation of the cessation of hostilities."

But the envoy devoted most of his public comments to criticizing Israel for holding a Cabinet meeting on Sunday in the Golan Heights, which Israel captured from Syria in the 1967 Middle East war and later annexed.

Russia's foreign minister meanwhile said the two sides meeting in Geneva should move to direct talks. Until now the two delegations have met in separate rooms, with a U.N. envoy shuttling between them.

Speaking to reporters in Moscow, Foreign Minister Sergey Lavrov denied allegations that Moscow and Washington were negotiating the departure of Syrian President Bashar Assad behind closed doors.

U.N. envoy Staffan de Mistura met with the government delegation in Geneva earlier on Monday and was to meet with the opposition later in the day.

Associated Press writers Jamey Keaten in Geneva and Nataliya Vasilyeva in Moscow contributed to this report.