BEIRUT — Syria’s military extended a unilateral cease-fire around the capital for another 24 hours Sunday, as violence began to subside across much of the country after days of heavy fighting concentrated in the northern city of Aleppo.

Aleppo, the country’s largest city and a key battleground in the civil war, was not covered by the cease-fire but saw less fighting Sunday. More than 250 people have died in shelling and airstrikes in the city over the last nine days, according to the Britain-based Syrian Observatory for Human Rights.

The government declared its own cease-fire around Damascus and the coastal Latakia region Friday after two weeks of escalating unrest. But more than three dozen rebel factions said Saturday they would not respect the truce unless the government agreed to extend it over the whole country.

Lieutenant General Sergei Kuralenko told Russian news agencies at a Russian Air Force base in Syria that Moscow’s forces were negotiating a cease-fire for the Aleppo province.

The Observatory said 859 civilians, including 143 children, died in Syria’s conflict in April, despite a partial cease-fire brokered by the United States and Russia in late February. That cease-fire disintegrated in recent weeks, largely over the fighting in and around Aleppo.

In Aleppo, as in the rest of the country, progovernment forces were responsible for most of the civilian causalities, according to the Observatory, which relies on a network of opposition activists inside Syria.

Secretary of State John Kerry appealed once more to his Russian counterpart for assistance in containing and reducing the violence, particularly around Aleppo.

‘‘We are talking directly to the Russians, even now,’’ Kerry said on his arrival in Geneva as he began talks Sunday with Jordanian Foreign Minister Nasser Judeh.

“The hope is we can make some progress, but the UN Security Council Resolution calls for a full country, countrywide, cessation and also for all of the country to be accessible to humanitarian assistance,’’ he said. “Obviously that hasn’t happened and isn’t happening.’’

‘‘We look for Russia’s cooperation,’’ Kerry said. “We obviously look for the regime to listen to Russia and to respond to the international communities’ powerful statement to the UN Security Council.’’

Kerry spoke at length on Friday with Russian Foreign Minister Sergey Lavrov to that end, and had been hoping to meet with Lavrov soon.

In Geneva, Kerry plans to meet Monday with the UN’s Syria envoy, Staffan de Mistura, and Saudi Foreign Minister Adel al-Jubeir.

Lavrov was not expected to be in Geneva, complicating Kerry’s efforts to make the case directly to the Russians for more pressure on their Syrian government allies to stop or at least limit attacks in Aleppo.