At least three people have been killed in a rebel rocket attack on a hospital in the northern Syrian city of Aleppo.

The attack was part of a shelling that left at least 19 people dead in government-controlled areas of the city on Tuesday, a monitoring group said.

Rebels and Syrian government forces have been battling each other with rockets and bombs across Aleppo and its outskirts for days now.

A partial truce is in effect in Syria but it does not cover Aleppo, the country's largest city and the scene of its worst violence in recent weeks.

In Sunday's violence, government forces carried out air strikes on Aleppo's rebel-held areas, including the Sakkour neighbourhood, after the rebels' rocket attack.

Syria's Ikhbariya news said three women were killed and 17 injured inside the hospital, located in the Muhafaza neighbourhood.

"[Dozens] martyred and wounded in rockets fired by terrorists at al-Dabbit Hospital," a news flash carried on state TV said.

The army said rebels had launched a widespread attack on civilian areas and hit the hospital.

It accused groups including al-Nusra Front, Ahrar al-Sham and Jaish al-Islam of being behind the shelling.

The UK-based Syrian Observatory for Human Rights also reported casualties at al-Dabbit Hospital, adding that the building had been heavily damaged.

The monitoring group said rebel shelling of government-held areas killed at least 19 people, including three children.