Syria's air force carried out strikes against rebels at more than double its usual rate on Monday, according to a monitoring group, ramping up its offensive near the capital while Washington strikes Islamic State fighters far away.
The intensified air strikes by President Bashar Assad's government will add to the fear among Assad's opponents that he is taking advantage of the US strikes to crush other foes, including the "moderate opposition" that Washington backs.
The United States says it does not want to help Assad's government despite bombing Islamic State, the most powerful group fighting against Damascus in a three year civil war. Washington aims to help arm moderates to fight against both Assad and Islamic State.
But within days of the start of US air strikes in Syria last month, Assad's government stepped up the tempo of its own air campaign against rebels closer to the capital Damascus.
Rami Abdelrahman, who runs the Britain-based Syrian Observatory for Human Rights, said the Syrian air force had struck 40 times on Monday in areas in Idlib and Hama provinces, including dropping oil drums packed with explosives and shrapnel. Typically Damascus has carried out no more than 12-20 raids a day.
Assad's government has raised no objections to the US bombing of Islamic State, which is mainly based in the east and north of the country, far from the most populous areas near Damascus and the Mediterranean coast.
Lebanese sources close to Damascus say Assad's government feels its interests have been helped by the US air campaign, which has allowed the government to focus its own military efforts on areas near the capital.