Malaysian Prime Minister Najib Razak pledged there will be no cover-up in the investigation of a debt-laden state investment fund and reiterated he is not involved in the murder of a Mongolian woman nine years ago.

Police have said there was no evidence to connect Najib in the murder but new allegations recently have tried to link him to the case.

In a surprise interview Thursday on national television, Najib also said he accepted criticism against his leadership and defended the government's move to revive detention without charges.

The interview appeared aimed at rebutting increasing criticism of him by former Prime Minister Mahathir Mohamad, who has warned there was "something rotten" in the country and that the ruling coalition may lose the next poll with Najib at the helm.