Aleppo: Fresh fighting hit Syria's Aleppo on Thursday, the first day of a promised Russian aid window the UN said was insufficient to bring relief for the city's desperate residents.
Even as Moscow pledged to pause strikes around the divided second city, it carried out raids further east on the Islamic State group bastion of Raqa that a monitor said killed 24 civilians.
Russia was meanwhile offered the possibility of joint operations against IS by Turkey, which has backed rebel groups against President Bashar al-Assad.
The offer came one day after crucial talks between President Vladimir Putin and Turkish counterpart Recep Tayyip Erdogan aimed at ending a crisis in ties.
A longtime ally of Damascus, Russia has provided air cover for pro-government forces for nearly a year, including in the escalating battle for Aleppo.
The city has been rocked by a recent surge in violence, with residents on both sides of the front line living in fear of being trapped by renewed hostilities.
The United Nations said Russia was considering expanding three-hour pauses in fighting every morning to bring in desperately-needed aid.
"Any pause obviously should always be seen and looked at with great interest, because a pause means no fighting, but three hours is not enough," said UN Syria envoy Staffan de Mistura.
Jan Egeland, who heads the UN-backed Syria humanitarian taskforce, said he was "hopeful" talks with Russia could lead to aid entering the city.
But rebels and regime forces clashed in southern Aleppo today, including during the period when the pause was meant to take hold, said the Syrian Observatory for Human Rights.
Rebels and jihadists broke a three-week government siege of the city's east on Saturday, opening a new route for goods through the southern outskirts.
AFP's correspondent in the east said trucks carrying food were unable to enter the city today because of intense bombardment.
An estimated 1.5 million people live in Aleppo, including about 250,000 in rebel-held districts.
Syrian's state news agency said army troops seized territory south of Aleppo today, adding that rebel fire killed four civilians in a government-held district.
But it made no mention of the "humanitarian windows" announced by Russia.
Fifteen of the only remaining doctors in the eastern half implored US President Barack Obama today to protect civilians from atrocities in their city.