Air strikes on Aleppo amid calm in other parts of Syria

In this image made from video and posted online from Validated UGC, a Civil Defense worker carries a child after airstrikes hit Aleppo, Syria, Thursday, April 28, 2016. A Syrian monitoring group and a first-responders team say new airstrikes on the rebel-held part of the contested city of Aleppo have killed over a dozen people and brought down at least one residential building. The new violence on Thursday brings the death toll in the past 24-hours in the deeply divided city to at least 61 killed. (Validated UGC via AP video) (The Associated Press)

A Syrian woman weeps as she holds an Arabic placard that reads "Aleppo has become the Aleppo of martyrs," during a protest in downtown Beirut, Lebanon, Saturday, April 30, 2016, against Syrian President Bashar Assad's military operations against areas held by insurgents around the country, mostly in the northern city of Aleppo that has been the main point of violence. (AP Photo/Bilal Hussein) (The Associated Press)

Protesters hold placards during a protest in downtown Beirut, Lebanon, Saturday, April 30, 2016, against Syrian President Bashar Assad's military operations against areas held by insurgents around the country, mostly in the northern city of Aleppo that has been the main point of violence. The Arabic placard read: "Enough, Aleppo is burning." (AP Photo/Bilal Hussein) (The Associated Press)

Two Syrian opposition monitoring groups are reporting government air strikes on insurgent-held neighborhoods of the northern city of Aleppo.

The Britain-based Syrian Observatory for Human Rights reported 20 separate air raids, killing at least two people and wounding others.

The Local Coordination Committees said the air raids killed one person and wounded others.

Contested Aleppo, Syria's largest city and once commercial center, has been the scene of intense shelling and air raids over the past nine days that killed nearly 250 people according to the Observatory.

The surge in fighting has caused the collapse of a two-month cease-fire brokered by the U.S. and Russia. It also has raised fears of an all-out government assault on Aleppo and warnings of a humanitarian disaster in the 5-year-old civil war.