A human rights group has accused Kenya of torturing and abusing suspects during its investigation of the bombing of a Mombasa hotel in 2002.
Fifteen people died in the bombing of the Mombasa Paradise Hotel
Some reported beatings by Kenyan police and one suspect was given electric shocks, Amnesty International said.
Others told Amnesty they were arrested without warrants, treated inhumanely and access to lawyers was withheld.
The Kenyan government denies abuse and said it had since brought in new rules for the treatment of terror suspects.
Amnesty International interviewed people arrested and subsequently released after the Mombasa attack and other terror-related investigations for its report.
The group said it had uncovered "a disturbing level of secrecy surrounding the arrests and detentions".
Suspects frequently reported being beaten by interrogators, some of whom were Kenyan and some apparently foreign, Amnesty said.
One man, named as Mohamed Ahmed Surur, said foreign intelligence services who questioned him had administered electric shocks until he passed out.
Other suspects told Amnesty they had been kept in filthy conditions with no access to medical care, family members or legal services.
The group said it was "concerned that the Kenyan authorities have failed to act in compliance with international human rights law and standards and Kenyan law in the investigations".
It accused Kenya of a "failure to respect the rule of law and to comply with the international human rights standards".
Kenyan government spokesman Alfred Mutua denied suspects were badly treated in detention and said Kenya had now brought in new laws to deal with terror suspects.
"The suspects... were not tortured," he told AFP news agency. "Since Kenya lacks legislation to deal with terrorism, which is a new phenomenon, the treatment... was misconstrued to be torture."
Four men have been charged with killing 15 people in the suicide bombing of the Israeli-owned Paradise Hotel in Mombasa in November 2002.
A group linked to the al-Qaeda network claimed responsibility for the attack.