Tunisia's president said Wednesday that the escape of five prisoners convicted of "terrorism" was a well-planned operation that had been in the pipeline for "months".

The government has urged Tunisians to be vigilant following the escape of the five from Mornaguia, Tunisia's largest prison, on Tuesday.

President Kais Saied said the prison break had been a "premeditated operation".

"All the elements indicate that the operation had been planned for several months," he said during a meeting with Interior Minister Kamel Feki.

"What happened is not acceptable, it is a failure for the security forces and certain individuals and they must be prosecuted," he added.

He accused certain people, who he did not name, of wanting to "harm the state".

Among the escapees was 44-year-old Ahmed al-Malki who was serving 24 years in prison on terrorism charges following the killing of opposition figures including Chokri Belaid.

The February 2013 assassination of Belaid — who was leader of the leftist Democratic Patriots' Unified Party — shocked the country and set off a political crisis that forced the Islamist-inspired Ennahdha party to cede the power it wielded since the 2011 revolution.

Several months later, Mohamed Brahmi, a left-wing member of parliament, was also killed. An investigation into both of their deaths has remained open ever since.

Both Belaid and Brahmi opposed Ennahdha, which dominated both parliament and government throughout most of the last decade.

The assassinations were claimed by jihadist militants.