Warplanes carried out air raids Sunday on several parts of northern Syria as a top opposition official warned that continued violations of a fragile cease-fire could jeopardize a planned resumption of U.N.-brokered peace talks.
The acts of violence came as Russia said a northern town held by a predominantly Kurdish militia came under fire from the Turkish side of the border.
Sunday's air raids came on the second day of a cease-fire brokered by Russia and the U.S., the most ambitious effort yet to curb the violence of the country's five-year civil war. The truce has been holding since it went into effect at midnight Friday despite accusations by both sides of violations.
The Britain-based Syrian Observatory for Human Rights said the airstrikes hit the villages of Daret Azzeh and Qobtan al-Jabal in Aleppo province. The group did not say whether the warplanes were Russian or Syrian.
The Local Coordination Committees said the warplanes were Russian.
The Observatory and the LCC also reported air raids on the northwestern town of Jisr al-Shughour saying a woman was killed and 12 others were wounded.
It was not immediately clear if the warplanes struck areas controlled by al-Qaida's branch in Syria, known as the Nusra Front. Both the Nusra Front and the Islamic State group are excluded from the truce.
Meanwhile Syria's state news agency said militants fired shells into government-held areas in the coastal province of Latakia from their bases near the Turkish border. The agency reported that the shelling killed and wounded a number of people, without giving further details.
Opposition activists and state media also reported clashes between troops and members of the Islamic State group mostly in the northern province of Aleppo. Still, both sides have said they will continue to abide by the truce.
Also Sunday, Riad Hijab, who heads the High Negotiations Committee, an umbrella for opposition and rebel factions, said in a statement directed to U.N. chief Ban Ki-Moon that Russian, Iranian and government forces have not stopped hostilities since the truce went into effect.
Hijab said there has been 24 cases of shelling and five cases of ground attacks. He added that Russian warplanes carried out 26 airstrikes on Sunday alone targeting rebels that are abiding by the truce.
"The repeated violations by the regime and its allies have killed 29 and wounded dozens," he said, adding that the opposition is abiding by the cease-fire and warning that "resuming the negotiations process in such circumstances would be difficult."
The U.N. Special Envoy to Syria Staffan de Mistura has called for a new round of indirect peace talks in Geneva on March 7, after the first round of talks collapsed earlier this month.
Meanwhile, the Russian military operating in Syria said it has information about an attack on the Syrian border town of Tal Abyad from Turkish territories with the use of large-caliber artillery and has asked the United States for an explanation.
Russia has set up a center for monitoring the truce at the Hemeimeem air base in Syria, where Russian warplanes are based.
On Saturday, members of the Islamic State group attacked the border town of Tal Abyad and the nearby village of Suluk that were captured months ago by Kurdish fighters, according to a Syrian rebel official.
Hours-long battles between Kurdish fighters and IS militants forced them out of Tal Abyad and other areas despite some presence of the extremists on the outskirts of the border town.
The Observatory said the battle of Tal Abyad lasted a full day and left 70 IS fighters, 20 Kurdish fighters and 10 civilians dead.
The head of the center. Lt. Gen Sergei Kuralenko, said Sunday that the suspected violation took place overnight and his center has turned to the corresponding U.S. center in Amman for an explanation, since Turkey is a member of the U.S.-led coalition, Russian news agencies reported.
In Turkey, President Recep Tayyip Erdogan said the cease-fire aiming to reduce the violence in Syria is only being partially implemented.
Erdogan expressed hope that "today or tomorrow this cease-fire will be secured and calm prevails in Syria" after noting that it is only being adhered to "in about one-third" of Syrian territories.
Erdogan made the remarks at a news conference in Istanbul prior to embarking on a trip to Africa.
The Syrian conflict has killed 250,000 people, displaced half the country's population and triggered one of the worst refugee crises since World War II.