A key figure in the struggle to succeed President Robert Mugabe, retired army general Solomon Mujuru, has died in a fire at his farm.

The state broadcaster reported the State Security Minister, Sydney Sekeramayi, as saying on Tuesday that Mujuru died in a "fire accident" in his farmhouse in the Beatrice district.

"Police forensics are investigating the cause of the fire, which engulfed the entire house," the Zimbabwe Broadcasting Corporation (ZBC) said.

Opposition media were quick to speculate on possible links between Mujuru's death and the struggle - reportedly between his wife, Vice-President Joice Mujuru, and the Defence Minister, Emmerson Mnangagwa - to succeed Mugabe as leader of the ruling Zanu-PF party.

ZimOnline said the circumstances of his death were "suspicious", while Nehanda Radio's website reported "several sources" as claiming that it was "both a political and domestic (sic) motivated incident".

Mujuru was widely reported during Zimbabwe's last election in 2008 to have wanted Mugabe to step down from power, first before the presidential vote and and then after Mugabe failed to secure election in the first round.

Mujuru, who fought Zimbabwe's liberation war under the nom de guerre "Rex Nhongo", was first arrested as a schoolboy, ZBC reported.

He joined the liberation struggle in the 1960s and rose to become acting commander of the Zimbabwe National Liberation Army in 1975. After liberation, he was appointed commander of the Zimbabwe National Army in 1981. From 1994 to 2000 he served as Member of Parliament for Chikomba District.

He had extensive business interests, including farms seized in the land reform process, and was involved in diamond mining.