A 98-year-old Nazi war crimes suspect, Hungarian Laszlo Csatary, has died while awaiting trial, his lawyer said.

"With the death of Csatary there are no further proceedings in this case," lawyer Gabor Horvath told Hungarian state news agency MTI.

Csatary died of pneumonia on Saturday morning in a Hungarian hospital after suffering from a number of medical problems, the lawyer said.

He allegedly helped deport 15,700 Jews to death camps during the spring of 1944.

Csatary was named in 2012 by the Nazi-hunting Simon Wiesenthal Center as its most wanted suspect.

He was charged by Hungarian prosecutors regarding what they said was his role as commander of an internment camp for Jews in Kosice, a town that is now in Slovakia. The Wiesenthal Center claimed he oversaw the deportations of Jews from Kosice to the Auschwitz death camp.

Prosecutors said in a statement that Csatary, a Hungarian police officer at the time, had "deliberately provided help to the unlawful executions and torture committed against Jews deported to concentration camps... from Kosice".

Csatary was convicted in absentia for war crimes in Czechoslovakia in 1948 and sentenced to death. He fled to Canada in 1949, claiming to be a Yugoslav national, and settled in Montreal, where he became an art dealer. He became a citizen in 1955. In 1997, his Canadian citizenship was revoked by the federal Cabinet for lying on his citizenship application. He fled the country two months later.

In 2012, Csizsik-Csatáry was tracked down in Budapest in July 2012 by reporters from the British Sun newspaper, with help from the Simon Wiesenthal Center, and was put under house arrest.

Csatary had denied the allegations against him, saying he was merely an intermediary between Hungarian and German officials and was not involved in war crimes.

Slovakia was seeking his extradition from Hungary so it could formally sentence him although, with the abolition of the death penalty, it intended to imprison him. The proceedings in Hungary were halted last month because of double jeopardy.