Syrian regime forces carried out air strikes and a rocket attack, killing at least five rescue workers and seriously injuring two others overnight in the west of Aleppo, the Syrian Observatory for Human Rights (SOHR) and volunteers working nearby said on Tuesday.
The regime forces targeted a centre for the Syrian Civil Defence, also referred to as the "White Helmets," who serve as the first responders in the opposition-held area, where medical infrastructure has been destroyed.
"The targeting was very precise," Radi Saad, a Civil Defence worker in the area, said.
"They were in the centre and ready to respond. When they heard warplanes in the area they did not think they would be the target."
There was no immediate comment from the Syrian regime.
Another Civil Defence member, Ahmad Sheikho, confirmed the attack and said ambulances along with vehicles that belonged to doctors were also hit.
Violence in Aleppo kills 30 people in past 24 hours
The Syrian Observatory for Human Rights announced on Tuesday that at least 30 people, including eight children, were killed in the past 24 hours in Aleppo.
The bombardment - by both the Syrian regime side and oppositions - of many neighbourhoods in the city also injured dozens more, the SOHR said.
The Observatory group also indicated regime air strikes and insurgent bombardments in Aleppo have killed dozens of people in the past several days.
On April 23, Syrian regime air strikes in the opposition-held town of Douma near Damascus, and Aleppo in the north killed 25 people and wounded many others.
The regime air strikes killed 25 and injured 40 others on April 22, in opposition-controlled parts of Aleppo.
A cessation of hostilities deal, which went into effect on Feb. 27, nearly collapsed as mediators struggled to get combatants to honour the deal in order to enable the peace talks in Geneva to proceed.
On Friday, UN Special Envoy to Syria Staffan de Mistura vowed to take the talks into next week despite a walkout by the main opposition High Negotiations Committee (HNC) in protest against the worsening situation on the ground.
The opposition's coordinator at the Geneva talks, Riad Hijab, said earlier it was unacceptable for talks to go on if the regime and its allies pushed on with sieges and bombing civilian areas.
UN Special Envoy to Syria Staffan de Mistura said on Thursday that around 400,000 people have been killed throughout the past five-years of civil war in Syria.