Syrian troops backed by tanks swept early Saturday into Banias, a hub of anti-regime protests, as residents formed human chains in a bid to halt the military operation, rights activists said. Electricity and communications were cut as the tanks entered along three axes heading towards the southern sector of the city on the Mediterranean coast, the bastion of the protesters. Protesters were resisting by forming human chains, the activists said, reached by telephone from Nicosia. Tanks also encircled the nearby town of Baida while an army boat patrolled offshore, they added. The military sweep into Banias in northwestern Syria comes two days after a convoy of 40 military vehicles pulled out of the southern town of Daraa, another protest centre, which the military had locked down since April 25. Human rights groups say that more than 600 people have been killed and 8,000 jailed or gone missing in the crackdown on protesters since demonstrations erupted in mid-March. The United States warned Friday it would take \"additional steps\" against Syria if it continues its brutal crackdown on protesters, a week after imposing tough sanctions on the Arab nation. The White House statement came after rights groups said Syrian security forces shot dead at least 26 protesters Friday during a huge \"Day of Defiance\" against the regime.