Former Bosnian Serb army chief Ratko Mladic was taken to hospital on Thursday after suddenly being taken ill during his trial at the Yugoslav war crimes tribunal.
"Mladic was feeling unwell and he was taken to a hospital as a precautionary measure," Nerma Jelacic, a spokeswoman for the International Criminal Tribunal for the former Yugoslavia, said.
Mladic's lawyer said the 70-year-old, who is on trial for genocide, war crimes and crimes against humanity for his role in Bosnia's 1992-1995 war, was in "bad shape".
The man known as the "Butcher of Bosnia" has complained before of health issues, with his lawyer Branko Lukic saying that Mladic has suffered three strokes and a heart attack in the past.
Last year he was also treated for pneumonia and suffers from kidney stones.
"He couldn't communicate with anybody and he couldn't open his eyes, he couldn't stand up," Lukic said after Mladic was taken ill, adding that his client was taken to hospital "but I don't know where".
He said Mladic was "in a good mood this morning, nothing was pointing (to the fact) that he was feeling unwell."
Prosecution witness David Harland, a former UN political advisor during the war, was giving evidence when judge Alphons Orie noticed something was amiss with Mladic and suspended the hearing.
Groups representing families of victims of the 1995 Srebrenica massacre, the worst atrocity on European soil since World War II, have in the past voiced concern over Mladic's health, saying they were afraid he might die before his trial was concluded.
The trial had resumed on Monday after being abruptly suspended because of prosecution irregularities on May 17, only a day after it opened in The Hague.
Mladic faces charges relating to the massacre in Srebrenica, as well as the terrorising of the Bosnian capital Sarajevo during 44 months of shelling and sniper fire which killed 10 000 people.
Former Bosnian Serb political leader Radovan Karadzic is also on trial before the ICTY, with both accused of being the masterminds of a criminal plan to rid multi-ethnic Bosnia of Croats and Muslims.
Prosecutors also hold Mladic responsible for taking UN peacekeepers hostage and allegedly ordering his troops to "cleanse" Bosnian towns, driving out Croats, Muslims and other non-Serb residents.
He was arrested in northeastern Serbia last year after 16 years on the run and subsequently moved to The Hague for trial.
Mladic has pleaded not guilty to the charges. If convicted, he could face life in prison.
Mladic's one-time mentor, former Serbian president Slobodan Milosevic died in The Hague in 2006 four years into his own war crimes trial.
In Bosnia, 520 victims of the Srebrenica massacre were buried Wednesday at a mass funeral on the 17th anniversary of the killings.
In all, almost 8 000 Muslim men and boys were slaughtered by Bosnian Serb troops who overran the enclave on July 11, 1995, when it was supposed to be protected by Dutch UN peacekeepers.