Robert Corbin was returned as head of the People's National Congress during a party congress on Saturday with 614 votes to 223 votes for his lone rival, attorney Winston Murray.

Several delegates who backed Murray alleged they were denied the right to vote, and other supporters were abruptly demoted from the status of eligible voting delegates to passive observers during the gathering of the PNC, which has its power base in Guyana's black population.

The party's general secretary, Oscar Clarke, told reporters Sunday that "the voting process was the most transparent possible," and dismissed accusations of fraud by supporters of Murray, who would have been the first East Indian leader of the PNC since its formation in 1955.

Murray told reporters he would issue a statement in coming days and did not respond to questions about his supporters' allegations.

Corbin, 61, suffered a heart attack earlier this year, but he campaigned vigorously to defend his post.

The PNC, which ran Guyana for 28 years until 1992, is trying to revive its flagging political fortunes against the governing East Indian-backed People's Progressive Party, led by President Bharrat Jagdeo. The next general election is scheduled for 2011.

Guyana's population of 700,000 is almost evenly divided between blacks, who mainly support the opposition, and people of East Indian descent, who mostly support the government.