Lima  - Former Peruvian president Alberto Fujimori was taken out of jail and to hospital in the early hours of Friday, following a week of colic and diarrhea.

Fujimori, 70, was to remain at the National Institute of Neoplastic Illnesses (INEN) in Lima, for doctors to determine the cause of his troubles.

In nearly 18 months in prison, the former Peruvian president has been admitted to the INEN several times, including one for removal of a carcinogenic tumour in his tongue and another to remove a benign cyst from his pancreas.

The latest admission to hospital came about a month before the court is expected to rule on a case against Fujimori for 25 killings and two kidnappings in 1991-1992, for which he faces up to 30 years in prison.

The trial has already occurred during his 18 months of preventive detention.

The former head of state insists he is innocent and that he neither ordered nor knew off any crime being committed. Several witnesses have contradicted his comments.

Fujimori - who holds both Peruvian and Japanese citizenship - ruled Peru from 1990 2000 and fled to Japan from the corruption allegations, from where he faxed his resignation back to Lima.

While Japan offered asylum because of his Japanese lineage, Fujimori was detained during a visit to Chile. Chile then extradited him back to Peru.