The United Nations has said that the conditional truce that began in Syria on Saturday has made "visible progress", despite clashes in some cities and areas, as Britain and France called on Russia and the Syrian government to stop attacking opposition groups.

Following a Franco-British summit on Thursday, French President Francois Hollande and UK Prime Minister David Cameron expressed concerns that rebel forces continued to be targeted in Syria.

"We ask all sides that are committing human rights violations, including Russia and the Syrian regime, to put an immediate end to the attacks against moderate opposition groups," they said in a joint statement.

The meeting came one day before Hollande and Cameron, along with German Chancellor Angela Merkel, are scheduled to discuss the truce in a conference call with Russian President Vladimir Putin.

"Tomorrow is an opportunity for the leaders of the UK, France and Germany to come together ... and make very clear to President Putin that we need this ceasefire to hold, to be a lasting one and to open the way for a real political transition," Cameron's spokeswoman told reporters.


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Meanwhile, Russia's defence ministry said in a statement on Thursday that it had registered 14 ceasefire violations in Syria over the past 24 hours.

The violations concerned the shelling of residential areas and Syrian government forces in the provinces of Damascus, Latakia, Hama and Deraa, it said.

'Visible progress'

It has been six days since the US-Russia-brokered truce was carried out but fighting continues in some parts of the country. Syria's government and the opposition - and their respective backers - have traded accusations over ceasefire breaches.

Despite the sporadic attacks, Staffan de Mistura, the UN envoy to Syria, said the level of violence in the county had been "greatly reduced" despite incidents in parts of Hama, Homs, Latakia and Damascus.

"In general, the cessation has been holding," he said on Thursday before entering a meeting of the UN-backed international task that is overseeing the truce.


EXPLAINER: What you need to know about the ceasefire in Syria


To summarise, de Mistura said, the situation is "fragile, success is not guaranteed, but progress has been visible".

He added that the progress laid out hopes of resuming peace talks between Syrian sides in the conflict on March 9.

The truce excludes areas under the control of the armed groups the Islamic State of Iraq and the Levant and the al-Nusra Front.

Late on Wednesday, a car bomb explosion killed the leader of the rebel group Syria Revolutionaries Front and 17 others in the village of al-Ashe in Quneitra province.

No group has claimed responsibility for the car bombing.

Source: Al Jazeera and agencies