Fighting raged on in Syria today, as a hoped-for ceasefire failed to materialise and Turkey intensified its shelling of Kurdish-led forces.
Further dampening hopes for an end to the conflict, the UN peace envoy admitted a February 25 date for a resumption of stalled peace talks was no longer "realistically" possible.
Key regime backer Russia meanwhile warned that recent comments by President Bashar al-Assad about retaking all of Syria were out of step with Moscow's diplomatic efforts.
On the ground, Turkey intensified its nearly week-long shelling of positions in Aleppo province, where it has sought to halt the advance of a Kurdish-led alliance against rebel forces.
The Syrian Observatory for Human Rights monitor said Ankara's overnight bombardment was the heaviest since it began targeting the Syrian Democratic Forces (SDF) on Saturday.
Turkey also expanded its fire, the Britain-based monitoring group said, hitting the Kurdish town of Afrin for the first time, where two civilians were killed and 28 wounded.
Ankara has been angered by the SDF's operation in Aleppo province, where it has seized key territory from rebel forces supported by Turkey.
Ankara considers the Kurdish People's Protection Units (YPG) that dominate the SDF to be an affiliate of the outlawed Kurdistan Workers' Party (PKK), which has waged a decades-long insurgency against the Turkish state.
It accuses the YPG and PKK of being behind a bombing that killed 28 people in the Turkish capital on Wednesday night, a claim denied by the Syrian Kurdish group.
Ankara fears the SDF advance in Aleppo province is intended to connect Kurdish-held areas in northern and northeastern Syria, creating an autonomous Kurdish region extending along most of its southern border.
Further east, SDF forces were advancing against the Islamic State group in Hasakeh province, the Observatory said.
The monitoring group said the alliance was now just five kilometres (three miles) from the IS stronghold of Al-Shadadi, and had cut two key routes leading from the town to Mosul in neighbouring Iraq and to Raqa, the jihadists' de facto Syrian capital.
The advance was assisted by heavy air strikes by the US-led coalition fighting IS, the Observatory said.
The coalition has backed the Kurdish-led SDF against IS, but Washington has cautioned the alliance against taking "advantage" of the situation in Aleppo, wary of angering its Turkish ally.
