South African national commissioner general Bheki Cele said police were investigating a link between wealthy businessman Shrien Dewani and the 2007 murder of Dr Pox Raghavjee.
Dr Raghavjee died during a carjacking in King William's Town, Eastern Cape, but the case reportedly remains open.
Publicist Max Clifford, who represents Mr Dewani, dismissed the possibility his client was implicated in either murder.
He said Mr Dewani, from Westbury-on-Trym, Bristol, met the doctor's widow Heather Raghavjee in South Africa after the murder.
But he said they had never previously met and Mrs Raghavjee had made the journey at the request of her daughter-in-law Alvita Raghavjee, who lives in the Bristol area and knows the Dewani family.
Public relations guru Mr Clifford added: "How flimsy and ridiculous this whole thing is. If it wasn't so tragic it would be a farce, a comedy."
Mr Dewani, 30, was released from Wandsworth Prison, London, on bail on Friday after his family came up with 250,000 security.
He is wanted by South African police for conspiracy to murder his new wife Anni, 28, who was killed after their taxi was seized by gunmen.
Taxi driver Zola Tongo accused Mr Dewani of offering to pay 15,000 rand (1,400) for his wife's murder and ordering it to appear like a bungled carjacking as they drove through the notorious township of Gugulethu.
Tongo's allegation formed part of a plea agreement drawn up with prosecutors at Western Cape High Court where he was jailed for 18 years earlier this week for his part in the killing.
Tongo has also alleged that Mr Dewani told him he had arranged a murder in a fake hijacking in South Africa before.
General Cele's spokeswoman said yesterday: "The investigation is ongoing even if it means linking Mr Dewani to other cases."
She confirmed a report the commissioner said police were investigating a link between Dewani and the Eastern Cape doctor's murder.
The commissioner told South African broadcaster SABC: "We are continuing investigations. There are new revelations about the Eastern Cape... So let's see what's going on."
At the High Court on Friday, prosecutor Ben Watson said "the net was closing in", arguing that Mr Dewani should not be granted bail "even on the most stringent conditions".