A couple and their five children were killed overnight in Syria's northern Aleppo province in strikes by the U.S.-led coalition fighting ISIS, activists said Monday. The Syrian Observatory for Human Rights, a Britain-based group, said the deaths raised to 148 the number of civilians killed in U.S.-led strikes in Syria since they began in September. The Observatory said the family was killed in a coalition strike on the village of Daly Hassan, in the northeast of Aleppo province. Their deaths "bring the number of Syrian civilians killed in coalition airstrikes since Sept. 23 to 148, including 48 children and 32 women," the group said. In May, the Observatory reported at least 64 civilians - nearly half of them children - had been killed in U.S.-led airstrikes in the village of Birmahle in Aleppo province. Syria's U.S.-backed opposition National Coalition urged an investigation into the overnight incident, noting that the available information "lends credence to report that it was a U.S.-led coalition airstrike." The Pentagon has generally denied that U.S.-led coalition strikes have killed any civilians, despite persistent reports of scattered civilian deaths. But on May 22, the head of the U.S.-led air campaign acknowledged that a November 2014 raid in Aleppo had killed two children - the first such admission from Washington. An investigation into the incident found the strikes were carried out in accordance with rules on targeting and determined there was no wrongdoing.