The leaders of Madagascar's Gen Z movement, whose protests helped topple President Andry Rajoelina, say they disapprove of the prime minister appointed by the country's new ruler.

Col Michael Randrianirina led a coup last week and was sworn in as head of state on Friday.

On Monday, he named businessman Herintsalama Rajaonarivelo as his prime minister. But in a statement on Facebook, Gen Z Mada said the appointment was made in a "non-transparent" manner and "without consultation".

Gen Z Mada added that the decision "runs contrary to the desired structural change" the movement was seeking.

The group has demanded to know how Rajaonarivelo was selected given what it says was his connection to the previous government.

"Our revolution will not be hijacked. The Malagasy youth are watching and mobilising," Gen Z Mada said.

Protests across Madagascar, triggered by frequent water and power outages, began almost a month ago.

Led by young people, they attracted other sections of society and morphed into wider demands for political change.

Rajoelina's calls for dialogue failed to quell the demonstrations and the president went into hiding. It was widely reported that he had fled abroad.

A week ago, Col Randrianirina, the head of the country's elite CAPSAT army unit, stepped in and announced the military had seized power.

After being sworn-in in civilian clothes on 17 October he thanked the young people who took to the streets.

"With a people in full fervour, driven by the desire for change... we joyfully open a new chapter in the life of our nation," he said.

Gen Z Mada has not said exactly what it will do if Rajaonarivelo's appointment is not explained or reversed, but the group has made it clear that it will continue to monitor the actions of the new administration.

"We will not allow the failed methods of the past to continue in a new form," Gen Z Mada's statement concluded.