BEIRUT, Lebanon — Dozens of people were killed in airstrikes on a market in northern Syria on Monday, according a monitoring group and a news agency run by activists. The attacks left rescuers and survivors digging late into the evening to search for residents still buried under the rubble.

There were at least three airstrikes on the market in Atareb, a town on the outskirts of Aleppo swollen by the arrival of refugees from nearby battles. It was the latest breach of a “de-escalation” agreement that has proved largely unenforceable. Aleppo is now controlled by the government.

A police station by the market was also struck, killing an officer, according to the Britain-based Syrian Observatory for Human Rights, monitoring group that tracks the conflict with the aid of a network of contacts in Syria.

At least 53 people were killed according to the Observatory, which said the market was hit by three separate strikes. There were at least five children and three women among the dead, it said. The Observatory said it could not determine whether the Syrian government or its chief backer, Russia, was behind the attack.