UN Secretary-General Ban Ki- moon on Wednesday voiced his concern at new arrests of high- ranking officials in Mali, and called on the ruling military junta to "refrain from any further actions that might undermine the effective restoration of constitutional rule in the country."

A statement issued here by Ban's spokesman said: "The secretary- general expresses his concern over the renewed wave of arrests of high ranking public officials in Mali at a time when numerous efforts are being undertaken to assist the country in overcoming the various challenges it is facing."

"The secretary-general calls for the immediate release of all those arrested and urges the junta to refrain from any further actions that might undermine the effective restoration of constitutional rule in the country," the statement said.

The ruling Malian military on Tuesday arrested the head of the country's biggest political party, hours after a former prime minister was detained by military personnel, reports said.

The arrests have raised concerns about whether Captain Amadou Sanogo is in fact transferring powers to the new civilian interim government as promised under an agreement reached with the Economic Community of West African States (ECOWAS), the regional bloc which is mediating to bring peace and stability to the west African country.

Also arrested between Monday night and Tuesday morning were former Defense Minister Sadio Gassama, former Prime Minister Modibo Sidibe, and Mahamadou Diagouraga, director general of the Malian police.

Those arrested also include Hamidou Sissoko, former chief of general staff during the regime of Toure, and Soumaila Cissem, chairman of the Union of the Republic and Democracy.

"These arrests are in contrast to other welcome developments that constitute important steps towards the full return to constitutional order, such as the appointment of Mr. Dioncounda Traore as interim president of Mali and his decision to nominate Mr. Cheick Modibo Diarra as the interim prime minister," the statement said.

"The secretary-general calls for the military junta to promptly complete the full transfer of power to civilian rule," the statement added.