SEATTLE – Those who have seen the dozens of photos say they are grisly: soldiers beside newly killed bodies, decaying corpses and severed fingers.

The photos, described in interviews and in e-mails and military documents, were seized by Army investigators and are a crucial part of the case against five soldiers accused of killing three Afghan civilians earlier this year.

Troops allegedly shared the photos by e-mail and thumb drive. Now 60 to 70 of them are being kept tightly shielded from the public and even defense attorneys because of fears they could wind up in the news media and provoke anti-American violence.

“We’re in a powder-keg situation here,” said Eugene R. Fidell, president of the National Institute for Military Justice and a military law professor at Yale University.

Since the images are not classified, “I think they have to be released if they’re going to be evidence in open court in a criminal prosecution,” he said.

Maj. Kathleen Turner, a spokeswoman for Joint Base Lewis-McChord near Seattle, where the accused soldiers are stationed, acknowledged that the images were “highly sensitive, and that’s why that protective order was put in place.”

At least some of the photos pertain to those killings. Others may have been of insurgents killed in battle, and some may have been taken as part of a military effort to document those killed, according to lawyers involved in the case.

Among the most gruesome allegations is that soldiers kept fingers from the bodies of Afghans they killed as war trophies. The troops also are accused of passing around photos of the dead and of the fingers.

Four members of the unit — two of whom are also charged in the killings — have been accused of wrongfully possessing images of human casualties, and another is charged with trying to impede an investigation by having someone erase incriminating evidence from a computer hard drive.

“Everyone would share the photographs,” one of the defendants, Cpl. Jeremy Morlock, told investigators. “They were of every guy we ever killed in Afghanistan.”

The graphic nature of the images recalled famous photos that emerged in 2004 from the Abu Ghraib prison in Iraq. Those pictures stirred outrage against the United States at a critical juncture.

In a videotaped interview with investigators, Morlock talked about hurling a grenade at a civilian as a sergeant discussed the need to “wax this guy.”

Morlock’s attorney, Michael Waddington, said the photos were not just shared among the defendants or even their platoon. He cited witnesses who told him that many at Forward Operating Base Ramrod in Kandahar Province kept such images, including one photograph of someone holding up a decapitated head blown off in an explosion.