WASHINGTON (Reuters) - The U.S.-led coalition fighting Islamic State militants said on Friday it had confirmed another 61 likely civilian deaths caused by its strikes in Iraq and Syria, raising to 685 the number of civilians it has acknowledged killing since the conflict began. The coalition said in a statement that during July, it had investigated 37 reports of civilian casualties. It found that only 13 of the reports were credible and there were an estimated 61 unintentional civilian deaths. The coalition is investigating another 455 reports of civilian casualties caused by its artillery or air strikes, the statement said. It has now acknowledged at least 685 civilian deaths due to its air and artillery strikes since the conflict began in August 2014. The deadliest incident investigated in July was a March 14 strike near Mosul, in which the coalition attacked an Islamic State position where fighters were firing at coalition allies. That strike is believed to have killed 27 civilians in an adjacent structure, the statement said. 