UPDATE 1-Niger leader dissolves constitutional court

* Tandja dissolves constitutional court

* Appoints eight new pro-referendum ministers

* Radio station taken off air

(Releads with dissolution of court, adds army reaction)

By Abdoulaye Massalatchi

NIAMEY, June 29 (Reuters) - Niger's president dissolved the constitutional court on Monday, hours after he appointed eight new ministers from parties that back his plan for a referendum on extending his stay in office.

The court said this month that President Mamadou Tandja's scheme was unlawful, but the president of the uranium-exporting West African country has vowed to press ahead anyway.

Tandja was due to step down when his term ends later this year, but he wants a referendum on Aug. 4 on whether he should be able to lead Niger for at least three more years.

The referendum plan has raised concerns among regional political bodies and Western donors, who fear it is a sign of back-sliding on democracy. It has also brought protests by unions and the opposition at home.