Prime Minister Andranik Margarian died Sunday of heart failure, government spokeswoman Meri Arutunian said. He was 55.

Margarian had been prime minister since May 2000. He was appointed in a politically tense period that followed an October 1999 armed attack on parliament that killed eight politicians including Prime Minister Vazgen Sarkisian.

The assassinated premier was first replaced by his brother, Aram, but President Robert Kocharian fired him and appointed Margarian amid rising discontent over Armenia's economic troubles.

Under the Armenian political system, the prime minister has mostly executive powers and is a much less powerful figure than the president.

Margarian, educated as a computer specialist, became active in opposition to the Soviet Union in the 1970s and was imprisoned for two years in that decade for espousing Armenian independence, according to his official biography.

Margarian is survived by a wife, two daughters and a son.