Syria's opposition said it will attend fresh peace talks next week, stoking hopes the war-ravaged country may be able to end five years of civil war and move toward elections in 18 months.
A nearly two-week truce has created a lull in fighting between the Russian-backed regime and non-jihadist rebels ahead of a new round of indirect negotiations due to start on Monday in Geneva.
The UN's envoy for Syria called Friday for elections in the war-ravaged country to be held by the middle of 2017.
But in a worrying development ahead of the negotiations, government raids reportedly killed seven civilians in Syria's second city, Aleppo.
The US State Department said Friday the truce "has produced a dramatic reduction in violence" but warned the regime was still carrying out attacks.
"Despite the reduction in violence nationwide, we remain deeply concerned by continued specific violations to the cessation of hostilities, including attacks on civilians and opposition forces by the regime and its supporters," spokesman John Kirby said.
The Riyadh-based High Negotiations Committee, the main Syrian opposition grouping, agreed on Friday to attend the UN-backed talks.
The HNC said it would focus on creating a "transitional governance body with full executive powers", but insisted Syrian President Bashar al-Assad "will have no place" in a future government.
A plan agreed by world powers last year called for six months of negotiations followed by a transitional government, a new constitution and elections within 18 months.
Last month Assad's regime announced it would hold parliamentary elections on April 13 instead, drawing criticism.
- 'Need to talk about Syria' -
UN envoy Staffan de Mistura has said "substantive" talks will begin Monday in Geneva and last no longer than 10 days.
"New elections... should be held 18 months from the start of talks, that is from March 14," de Mistura told Russia's RIA Novosti state news agency, in comments translated into Russian.
In addition to planning the polls, the focus in Geneva will be on the formation of "an inclusive new government" and a new constitution, said the envoy.
A source close to Syria's government told AFP this week its delegation would be attending the talks.
The complex war, which is to enter its sixth year next week, has killed more than 270,000 people and displaced half the population.
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Russia on Friday urged the UN to include Kurds, which have been a major force fighting jihadist groups such as Islamic State and control about a tenth of Syrian territory.
Excluding them would be "a most serious infringement of the rights of a large and significant group living in Syria", Foreign Minister Sergei Lavrov said.
The last round of UN-sponsored talks collapsed in February after the government began a fierce Russian-backed offensive in Aleppo province.
US Secretary of State John Kerry met Saudi Arabia's King Salman and his most senior ministers Friday for talks on Syria, where both countries are key supporters of rebel forces.
"I think we need to talk about Syria," Kerry said.
The chief prosecutor for the Yugoslav war crimes tribunal, Serge Brammertz, said Friday that those behind atrocities in Syria must eventually be held to account.
- 'Glimmers of hope' -
The UN's top humanitarian chiefs welcomed "fragile glimmers of hope" in Syria after the ceasefire allowed more aid deliveries.
"Fewer bombs are falling, humanitarian access has opened up in some places, negotiators from all sides are preparing to come together and talk," they said in a joint statement.
But they warned this was "just not enough".
Britain-based monitor the Syrian Observatory for Human Rights described government air strikes that killed at least seven civilians in Aleppo as "the most serious violation in the city since the truce came into effect".
An AFP correspondent in Aleppo said the raids struck a mosque.
Hundreds of demonstrators took to the streets across Syria after Friday prayers for the second week in a row.
In Maaret al-Numan, northwest Idlib province, dozens of protesters waving the three-starred, tricolour uprising flag briefly clashed with members of Al-Qaeda affiliate Al-Nusra Front.
In a video posted online, motorcyclists waving Al-Qaeda's black flag pulled up and attempted to drown out the singing with calls of "Allahu akbar," or "God is greatest".
But the crowd pushed the Al-Nusra members out, chanting, "the Syrian people are one!"