UN chief Ban Ki-Moon said on Saturday that Syrian authorities have "manifestly failed" to protect civilians and called on the international community to act to stop the violence. “The Syrian government has manifestly failed to protect civilians and the international community has a collective responsibility to live up to the UN charter and act on its principles," Ban said during a visit to Croatia’s Brijuni Island as part of a week-long Balkans tour.

Ban added that he was “deeply distressed by the rising death toll and the number of people forced to flee their homes” as heavy clashes between troops and rebels raged in Syria’s second city Aleppo on Saturday, according to activists.

The capital Damascus was calm after a day of fierce fighting.

Ban praised the United Nations’ Security Council vote a day earlier to allow a “final” 30-day mandate extension to the troubled UNSMIS observer mission charged with overseeing a peace plan for Syria. “The unanimous vote (Friday) on resolution 2059 is a constructive sign. Now the council must redouble efforts to forge the united way forward and exercise collective responsibility under the charter of the UN,” he stressed. The UN secretary general also called on the parties in Syria, government and opposition forces alike, “to stop armed violence without any conditions.”

“The extension of the UNSMIS mandate for only 30 days is a strong signal that the onus is above all on the parties, with the Syrian government in the first place who must stop the killings and the use of heavy weapons against population centres,” Ban said.

Heavy clashes raged between Syrian troops and rebels on Saturday, with at least 24 people killed nationwide, as the clock ticked down on a 30-day “final” extension of a troubled UN observer mission.

Activists reported fierce fighting in the country’s second city Aleppo, with regime forces shelling several neighbourhoods, as at least seven people were reported dead in the capital, most of them killed by snipers.

Syria needs a transitional government soon which would represent the diversity of its society, French Foreign Minister Laurent Fabius said in a statement issued on Saturday.

“Time has come for the opposition to get going and take over the reins of the country,” said Fabius.

He said he could organise a meeting of ministers in Paris “to consolidate efforts by Arab countries to build tomorrow’s Syria.”

Fabius said he was in contact with Arab League chief Nabil Al Arabi, Qatari Prime Minister Sheikh Hamad Bin Jassem Al Thani and others to find a solution to the 16-month crisis in Syria.

Syrian rebels took control of the main crossing between Iraq and Syria along the two countries’ northern border on Saturday, the governor of the Iraqi province of Nineveh said.

“Iraqi officials from the crossing called me and they said that at 5:00 pm (1400 GMT), some gunmen took control of the Yaribiyah crossing and they were informed that the crossing is now in the hands of the Free Syrian Army,” Atheel Al Nujaifi said, referring to the Rabiyah crossing by its Syrian name.

Syrian troops and tanks were surrounding a prison in central Syria and firing on it on Saturday after prisoners mutinied, an activist said.

Prisoners took over one of the two wings of Homs central prison after several guards defected, activist Hadi Abdullah said in Beirut via Skype.