Iraq has so far exhumed the remains of 597 people believed to have been executed by Islamic State jihadists in the so-called Speicher massacre, the human rights minister said Wednesday.

"The remains of 597 Speicher martyrs have been exhumed," Mohammed al-Bayati told journalists in Baghdad.

In June 2014, armed men belonging or allied to the Islamic State (ISIS) group captured hundreds of young, mostly Shiite recruits from Speicher military base, near the northern city of Tikrit.

They were then lined up in several locations and executed, as shown in pictures and footage later released by ISIS.

Some were pushed into the Tigris river, others hastily buried in locations that were discovered when government and allied forces retook Tikrit from ISIS in April.

The highest estimate for the number of people killed in one of the worst atrocities committed by ISIS stands at 1,700.

Combined with a call by the country's top Shiite cleric, Grand Ayatollah Ali al-Sistani, for Iraqis to take up arms against ISIS, the Speicher massacre played a key role in the mass recruitment of Shiite volunteers to fight the jihadists.