Students were among 304 people killed when the ferry sank in

The parents of 92 students who died in the South Korea ferry disaster have been sent letters calling up their dead sons for military service.

The boys were among 304 people killed when the Sewol ferry, carrying 476 people, sank off the south-western island of Jindo in April 2014.

But now, the parents of 92 youngsters who attended Danwon High School in Ansan have received letters telling their dead sons to attend physical examination assessments before their conscription, which is compulsory for South Korean men.

Tragedy: Rescue helicopters pictured flying over the Sewol ferry as it sank off the south-western island, Jindo

Students from Danwon High School pay tribute to their peers who died when the ferry sunk in April 2014

A local mayor posted a message on Twitter saying a relative of one of the victims had cried all night after receiving the notice.

The Korea Herald quoted a Facebook post of the father of one boy, which read: 'How could they not have bothered to confirm my son's death?

'The bureaucracy is so speedy and effective - only for this kind of thing to happen.'

The Military Manpower Administration sent out the notices earlier this month to every man born in 1997, The Telegraph reports.

It has apologised but said it tried to obtain a complete list of the victims, explaining they were never officially registered as deceased.

A spokesman for The Military Manpower Administration said: 'We have tried to exclude the victims killed or missing in the Sewol disaster in the mailing list since July 2014. But we had no choice but to send the notices because we could not secure a list of the victims.

'We didn’t send notices to the 27 victims whose deaths were formally registered.'

Korea JoongAng Daily reports that by law, the public office handling a death case must report to the regional director where the dead person is registered.

More than 300 people killed when the Sewol ferry, carrying 476 people, sank off the island of Jindo in 2014

In the ferry disaster, the head of the coast guard was required to report to the Mayor of Ansan to process the death reports.

This did not happen because the coast guard was disbanded after the tragedy, according to Korea JoongAng Daily.

The Military Manpower Administration said the high school and the Office of Government Policy Coordination would not provide a list of names either.

The ferry tragedy shocked and enraged the country as it became clear that it was almost entirely man-made - the result of an illegal redesign, an overloaded cargo bay, an inexperienced crew and an unhealthy nexus between operators and state regulators.