Washington, April 23 -- The U.S. has admitted to more civilian casualties in its airstrikes against alleged Daesh (ISIL) positions inside Syria and Iraq between September and February, amid reports that the Pentagon has increased civilian death tolerance in the two countries.

According to a statement on Friday by the U.S. Central Command (CENTCOM), in the five-month period, a total of 20 civilians were killed and 11 others were injured as a result of air raids by the U.S.-led coalition which started its aerial campaign in August 2014.

The new announcement raises the official tally of civilians killed in the campaign to 41, with 28 more wounded. According to a USA Today report earlier this week, the Pentagon has passed new rules allowing higher levels of allowable civilian casualties in its military campaign against Daesh.

Six Pentagon officials, all speaking on condition of anonymity, told the newspaper that the Pentagon has delegated more authority to U.S. Army Lieutenant General Sean MacFarland, head of the U.S.-led coalition against Daesh in Iraq and Syria, to approve targets when civilians could be killed.

Meanwhile, Airwars, a UK-based airstrikes monitoring group, says the real number of U.S. civilian victims exceeds 1,000 people as the U.S. and its allies have carried out more than 12,000 plane and drone strikes in Iraq and Syria, dropping some 40,000 bombs.