The Syrian Observatory for Human Rights says the Syrian army and its allies have launched a big attack overnight on rebels in a town south of Aleppo.

The pro-opposition monitoring group said air strikes, artillery and rockets were being used in the attack. The Syrian army says the attack is a response to rebel violations of the cessation of hostilities agreement.

The al Qaeda-linked Nusra Front shot down a Syrian warplane in the area on Tuesday, capturing a pilot. Meanwhile, the monitoring group said a pregnant woman and three children were among 18 civilians killed when Syrian rebels shelled a Kurdish neighborhood of Aleppo. It said 70 people, including 30 children, were wounded in Tuesday's attack.