The 66-year-old Bosnian, who took over from Brazilian Zico as head coach following the 2006 World Cup finals in Germany, was rushed to hospital after collapsing in the early hours of Friday morning.

The Sarajevo-born coach was found by his wife and son and has been diagnosed with an acute cerebral infarction.

"Osim is receiving treatment in the intensive care unit and we've heard that his condition is unstable," said JFA president Saburo Kawabuchi. "We are not prepared to talk at this stage about the long-term prospects.

"This has come as a shock to the JFA. We hope he makes a full recovery."

Osim, head coach of Yugoslavia at the 1990 World Cup finals, has been working in Japan since 2003, when he joined J.League side JEF United Chiba before taking up the position with the national team.

Osim's most recent public engagement was on Wednesday evening, when he watched J.League champions Urawa Reds defeat Sepahan from Iran in the final of the AFC Champions League at Saitama Stadium.