Zimbabwe's 91-year-old president, Robert Mugabe, accidentally read the wrong speech at the opening of parliament on Tuesday.

Robert Mugabe

Robert Mugabe

Mr Mugabe delivered the speech for the first time as a state of the nation address last month, when he was booed and heckled by opposition MPs, who sang protest songs against his 10-point plan to solve the country's economic crisis. This time, however, the opposition was silent, while Zanu-PF party supporters clapped at regular intervals during the speech.

The BBC reports that at least six opposition MPs of the Movement for Democratic Change party (MDC) had received intimidating text messages from a sender called "Death", warning them to behave: "Warning: Immunity ends in parliament... act wisely by not disturbing the proceedings of parliament."

Obert Gutu, a spokesman for the Movement for Democratic Change, said that the delivery of an old speech proves that president is too old to govern.

"We have a 91-year-old president who has a fading memory, who, if he had sharpened up his memory would have immediately picked it up that this speech was actually a stale speech," he said.

"The rigours of his presidential office are too much for him, and ... at the advanced age of 91 (he) should do the honourable thing and step down from office."