ITV Wales understands that Rhodri Morgan collapsed and died while cycling in the lanes near his home.
South Wales Police say officers were called to an incident involving the former First Minister in the Wenvoe area shortly after 5pm on Wednesday evening.
Officers and paramedics went to the scene after reports that a man had been taken ill, but say Mr Morgan was pronounced dead at the scene.
Friends have told ITV Wales "he died doing what he loved".
The coroner has been informed.
Family, friends and colleagues shared memories of the 77-year-old, who died on May 17 after collapsing while cycling near Cardiff.
The funeral of the former First Minister is open to the public and can be viewed live.
The former First Minister died two weeks ago whilst out cycling near his home in Cardiff. Today his funeral will be open to the public.