Iraq has exhumed the remains of 164 people believed to have been massacred by jihadists from mass graves in Tikrit, the human rights ministry said Monday.

“Search teams have discovered the remains of 164 (victims) so far in four mass graves during work over the past week,” ministry spokesman Kamel Amin told AFP.

He said documents and mobile phones that have been found indicate the dead are victims of the infamous Speicher massacre, named for the military base near which up to 1,700 mostly Shi’ite recruits were abducted by the Islamic State (ISIS) jihadist group last year.

But DNA testing is required to confirm their identities, Amin said.

The remains were discovered inside former president Saddam Hussein’s palace compound in Tikrit, which officials say holds 10 mass graves, while three more are located outside it.

The killing of the recruits – which ISIS documented in photos and videos posted online – stoked widespread anger and helped rally support for the battle against the jihadist group.

The mass grave sites were discovered after Iraqi forces retook the northern city of Tikrit earlier this month in their biggest victory so far against ISIS.

ISIS led an offensive last June that overran large areas north and west of Baghdad, but Iraqi security forces and allied paramilitaries have succeeded in regaining significant ground.