SEOUL (REUTERS) - South Korea's military faced more criticism on Tuesday, a day after the capture of a wounded soldier who killed five members of his own unit, over its decision to use a decoy soldier to divert attention when moving him to hospital for treatment.

The conscript was captured on Monday after he shot himself in the chest ending a prolonged standoff with troops. He is accused of killing five soldiers and wounding seven at a base where he threw a grenade and opened fire late on Saturday.

TV footage showed a military ambulance arriving at the emergency room of the hospital in Gangneung, the eastern city near the scene of the attack, and a person on a stretcher believed at the time to be the suspect.

The person was later revealed to be a decoy, wrapped in a blanket from head to toe, while the injured conscript was being brought in through a basement loading dock.

The ploy was orchestrated at the request of the hospital to avoid chaos, a military official said on the condition of anonymity, amid all the press interest in the case.

"We received the view from the hospital that a stand-in patient would be needed, and we operated a separate ambulance with a stand-in," the official said.

Several calls seeking comment to an official who was designated to speak for the hospital went unanswered.

The use of a stand-in nevertheless raised questions about the military's judgment. "Where is the real soldier, then?" one Twitter user said.

"What are we to believe now? It's unbelievable they would use a stand-in for that soldier," another said.

The incident comes amid criticism that the military has allowed discipline to become lax in some units and that it had failed to prevent previous tragedies where soldiers, suffering personal problems, have shot fellow soldiers.

The soldier involved the weekend drama was described by an official as an "introvert" with earlier concerns over his psychological health. But he was deemed fit to be deployed to the outpost after passing a test in November.

The Defence Ministry said the soldier, who was identified by surname Lim, left a note before he was captured apologising to his family but that there was no mention of personal problems with his fellow unit members.