Warplanes struck a town in northern Syria where a chemical attack killed scores of people earlier this week, Syrian opposition activists said on Saturday.

The Britain-based Syrian Observatory for Human Rights said Saturday’s airstrike on the eastern side of Khan Sheikhoun killed a woman, marking the first death in the town since Tuesday's chemical attack that killed 87.

The Local Coordination Committees, another monitoring group, said the airstrike was carried out by a Russian warplane. It said the woman who was killed had fled to Khan Sheikhoun from her hometown of Latameh in central Syria.

In response to Tuesday’s attack, the U.S. struck an airbase in central Syria two days later, killing nine people.