Air strikes from Syrian government warplanes have hit a school in the main northern city of Aleppo, killing at least five children and four other civilians, a monitoring group has said.
The London-based Syrian Observatory for Human Rights, which monitors the conflict through a network of local activists, said the strike on Sunday killed five children, three female teachers and one man.
It added that a number of people were seriously wounded and the death toll was likely to rise.
The latest strike comes a day after the monitoring group and Syrian state television reported shelling by Syrian rebels on a government-held neighbourhood in Aleppo.
Footage aired on Syrian state television on Saturday showed damaged buildings and injured people being treated at the overcrowded local hospital.
State TV said the shelling on the predominantly Christian and Armenian neighbourhood of Sulaymaniyah in Aleppo killed nine people, wounded another 50 and damaged several buildings. It said dozens of people were still trapped under rubble.
The observatory said the shelling killed 27 people and wounded many more.
Hours after the shelling, helicopter gunships struck a market in Aleppo's rebel-held neighbourhood of Maadi in an apparent retaliation by the Syrian government, according to the observatory and the opposition-run Aleppo Media Centre.
The observatory said the air strike killed 10 people and wounded dozens, some seriously.
The Aleppo Media Centre reported casualties but did not provide a precise toll.
|Infographic Syria: Communities Besieged [Al Jazeera]
News of the air strikes came as the head of UNRWA, the UN agency for Palestinian refugees, planned an "urgent mission" to Damascus amid concerns over the humanitarian crisis in the Palestinian camp of Yarmouk, most of which has been captured by the Islamic State of Iraq and the Levant [ISIL] group.
Pierre Krahenbuhl was to discuss the situation in Yarmouk and meet with displaced refugees.
UNRWA said in a statement the visit was prompted by "its deepening concerns for the safety and protection of some 18,000 Palestinian and Syrian civilians, including 3,500 children" who remain in the Yarmouk camp.
"Yarmouk remains under the control of armed groups, and civilian lives continue to be threatened by the effects of the armed conflict in the area," it said.
On April 1, ISIL launched an assault on the Palestinian armed group Bait al-Maqdis, which is one of the many factions that share control of the district.
After the government claimed that ISIL took over most of the camp - which has been denied by local activists - government forces stepped up their shelling of the district, further worsening the camp's humanitarian crisis.
The Syrian observatory reported on Thursday that since April 4, government helicopters had dropped 36 barrel bombs, which are highly indiscrimate and destructive explosives, on Yarmouk.
Krahenbuhl, who will meet displaced refugees on Sunday in a school near the camp, will discuss "with the government of Syria... peaceful approaches to addressing the humanitarian consequences of the situation in Yarmouk".
He will also meet with deputy special envoy Ramzy Ezzeldin Ramzy, who was sent by UN chief Ban Ki-moon on Friday to Damascus.
Since 2012, Yarmouk has seen ongoing clashes between government forces and Syrian rebels, with Palestinian factions divided and fighting on both sides.
The sprawling district, once home to 160,000 Palestinians as well as Syrians, has endured an army siege since 2013.
Source: Al Jazeera and agencies