There is credible evidence that U.S. military airstrikes in Somalia have killed or wounded nearly two dozen civilians, an international human rights group said Tuesday, charging that the Pentagon is not adequately investigating potential casualties.

U.S. Africa Command officials immediately disputed the allegations laid out in a report by Amnesty International, and insisted that the military has investigated 18 cases of possible civilian casualties since 2017 and found that none were credible.

But Amnesty researchers who investigated five air strikes in detail reported at least 14 civilians had been killed, raising fears the total dead in the scores of attacks may be far higher. "The attacks appear to have violated international humanitarian law, and some may amount to war crimes," Amnesty said in the report, titled "The Hidden U.S. War in Somalia." The study is based on 150 interviews including witnesses, family members of those killed and security experts. Their reports were corroborated by satellite imagery, photographs of the deep craters of the explosions, as well as munition fragments collected from the sites.

U.S. strikes, which included missiles fired by manned aircraft as well as drones, targeted the al-Qaida-linked al-Shabab group in Somalia. There are 500 to 600 U.S. troops in Somalia at any time. The pace of U.S. airstrikes in Somalia has escalated during the Trump administration, from 47 in all of 2018 to 28 already this year. So far more than 230 militants have been killed in 2019, compared to 338 killed in all of 2018.