A rights group says it counted 21 unidentified bodies in a hospital morgue believed to have been retrieved from the River Yala in western Kenya.
Kenyan police said they have launched an investigation after badly decomposed bodies, some of which bore signs of torture, were found in a river.
Nineteen cases of bodies being found dumped in the Yala had been reported over the past two years, police said on Wednesday.
"This number represents a cumulative body count over the stated period contrary to media reports insinuating all the incidences are a recent occurrence," police spokesperson Bruno Shioso said in a statement.
The statement came after a rights group said it counted 21 unidentified bodies in a hospital morgue.
Shioso said a team of investigators has been assigned to the case but that no-one has claimed the bodies despite repeated appeals.
"To speed up the identification of the victims ... a special forensic investigation team from the Directorate of Criminal Investigations headquarters has been dispatched to the scene," he added.
'Bodies in sacks'
A Kenyan rights group said it counted 21 unidentified bodies — all men — in a morgue that workers there said had been retrieved from the River Yala in a scenic area of western Kenya.
"Some of the bodies were tied with ropes, others had deep cuts and others had polythene bags on the heads," Haki Africa Executive Director Hussein Khalid said in a statement after the visit on Monday.
"The mortuary attendant informed us that at least 10 bodies were found in individual sacks, which were properly stitched like parcels."
Morgue officials told the activists they keep unclaimed corpses for 90 days before burying them — suggesting the bodies may have been found over the past three months.
Cases of enforced disappearances, sometimes blamed on police and security services, are not uncommon in the East African country, and incidents of extrajudicial killings are also rife.
Haki Africa said the dumping of the bodies was "disturbing" and called for police in the area to be investigated "to ascertain whether or not there was involvement of the police in the killings".