The Local Coordination Committees, which helps organize anti-government protests, urged people to take to the streets and start a general strike to protest the killings.
Assad has brushed off the criticism as foreign interference.
Most were killed in shootings by security forces at anti-government rallies.
The figure was confirmed by the London-based Syrian Observatory for Human Rights, which cited hospital officials in Hama.
In 1982, Assad's father, Hafez Assad, ordered the military to quell a rebellion by Syrian members of the conservative Muslim Brotherhood movement. The city was sealed off and bombs dropped from above smashed swaths of the city and killed between 10,000 and 25,000 people, rights groups say.
Syrian President Bashar Assad said his country is capable of foiling any conspiracy to undermine its national unity, the state-run news agency SANA reported early Monday.
-- Syrian government forces attacked the city, razing the old quarters of Hama to crush the armed uprising by the Brotherhood, who had taken refuge there.
-- In June, activists said Syria forces killed at least 60 protesters in the city, in one of the bloodiest days of the uprising against Assad.