The Kenya government says security agencies are on high alert following the escape of three terror convicts from Kenya's most secure prison.

One of those who escaped was convicted for the 2015 attack on Garissa University in which close to 150 people died.

Another had been convicted for a foiled assault on Kenya’s parliament, and the third for crossing into Somalia to join al-Shabab.

Agencies are closely monitoring the country's borders, while seven prison wardens have been arrested.

Detectives are investigating how people described as dangerous escaped from the Kamiti prison - the country's most guarded detention facility about 20km north-east of the capital, Nairobi.

In a statement, Interior Minister Fred Matiangí said investigators looking at whether the prison break was a result of incompetence and laxity.

More arrests and prosecutions could follow.

A countrywide manhunt is under way, and a $550,000 (£408,000) bounty offered for their recapture.