The U.S. military said Friday that its airstrikes against the Islamic State group in Iraq and Syria killed two civilians and wounded four others last July.

The report from the U.S. Central Command updated an announcement two weeks ago that U.S. airstrikes during two earlier months in 2015 had killed eight civilians and wounded three other released Friday. It brings the total to 10 deaths reported by the military within the last month.

The report, released at the command’s headquarters in Tampa, Florida, included brief details of the five strikes, recounted in military jargon.

Referring to a bombing run on July 11 near Raqqa, Syria, a city controlled by IS extremists, U.S. military officials said: "A post-strike review revealed a secondary explosion from a vehicle crossing a bridge nearby the intended target; this explosion resulted in one civilian likely killed."

An independent organization that monitors civilian casualties,, said "the actual toll from these five events is between 14 and 21 casualties."

The not-for-profit group, funded by charitable organizations and human rights activists, estimates coalition airstrikes have killed between 803 and 1,127 civilians since August 2014 – far more than military authorities have reported.

The Pentagon investigates all U.S. airstrikes and issues its assessment of incidents where civilians died, although such studies are often released long after the raids took place.

Recent U.S. news reports have suggested the military's "zero tolerance" policy for civilian casualties recently was relaxed to allow more intensive action against Islamist fighters in Syria and Iraq. Since IS and other groups frequently locate their forces in the midst of civilian populations, a stepped-up U.S. offensive likely would result in more civilian casualties.

VOA's Pentagon correspondent, Carla Babb, and national-security correspondent Jeff Seldin contributed to this report.