Zimbabwe's President Robert Mugabe has warned the country's security services not to get involved in politics.

Army, police and intelligence officers were taking sides in the ruling Zanu-PF party's infighting over the battle to succeed him, he said.

Such factionalism was destructive, the 91-year-old leader said.

He made these remarks off the cuff to Zanu-PF's annual gathering, as he first began reading the wrong speech, before realising after about 30 seconds.

Mr Mugabe quickly recognised that the address was one he had given on Wednesday to the party's central committee.

In September at the opening of parliament, he read out a whole speech that he had given the previous month in a state-of-the-nation address.

Loyalties over the succession within Zanu-PF appear to be split between the president's wife Grace Mugabe and his deputy Emmerson Mnangagwa.