Former Sierra Leone Vice-President Samuel Sam-Sumana, who was fired by the president in March, petitioned the Supreme Court on Thursday to block his replacement from carrying out his duties pending a final ruling on the legality of his dismissal.

President Ernest Bai Koroma dismissed Sam-Sumana, claiming he had abandoned his duties by requesting asylum at the U.S. Embassy in the capital Freetown. The ruling All People's Congress had earlier accused him of creating his own political movement and expelled the party.

Koroma later chose Victor Bockarie Foh to replace Sam-Sumana over the objections of the opposition, which said he is not eligible to hold the position.

Thursday's hearing was the first before the Supreme Court on the matter.

"The President has unconstitutionally removed a constitutionally elected vice president and unconstitutionally appointed another person," JB Jenkins Johnston, an attorney for Sam-Sumana, argued before the panel of five judges.

Koroma said he had acted legitimately using supreme executive authority, but Sam-Sumana's lawyers are challenging whether the president's decision complied with Sierra Leone's constitution.

As a provisional measure, they sought on Thursday to bar Foh from occupying the office of vice president.

The court adjourned pending a ruling on the motion, though no date was given for the decision.

For much of its history since gaining independence from Britain in 1961, Sierra Leone has been plagued by political instability, including a series of military coups and a 1991-2002 civil war.

The head of the army last month ordered soldiers to remain in their barracks and warned them to steer clear of the political crisis that has erupted following Sam-Sumana's dismissal.