Tigran Sargsyan announced his move on Facebook today, but did not give his motives.
Edward Sharmazanov, a deputy speaker of parliament and member of the ruling Republican Party, said Armenian President Serge Sarkisian accepted the prime minister's resignation.
The new prime minister will be nominated by the ruling party. He's to be named within 10 days, according to the Armenian law.
The resignation of Sargsyan, who served as prime minister since 2008, is widely believed to be linked to a pension reform that has drawn public criticism.
