Authorities in Kazakhstan say that they are investigating the drowning of four Kazakh soldiers during an ill-fated military exercise on the Caspian Sea.

Defense Minister Imangali Tasmagambetov visited the Caspian city of Aqtau on September 19, where an amphibious landing exercise went wrong on September 18.

He reportedly relieved four regional military officials of their duties.

Meanwhile, Kazakhstan's military prosecutor has opened an investigation into the deaths of the soldiers, who all drowned when four BTR-80 armored personnel carriers sank in rough waters during the attempted amphibious landing.

A Defense Ministry statement said initial findings suggest the drownings were the results of "a poor decision when practicing an amphibious landing in the absence of landing equipment."

Three of the soldiers -- identified as Bauyrzhan Zholdabay, Asylzhan Makhambetov, and Bagytzhan Kalybay -- were 19 years old.

The fourth soldier who drowned, Amir Adylov, was 23.

With reporting by AFP