BEIRUT – Troops in tanks and armored vehicles entered a key oil-industry city on Syria’s Mediterranean coast Saturday, taking up position in a hilltop Crusader castle and cutting off power and phone lines. An activist said three women protesting the crackdown were shot dead.

The move against Banias, which had become a bastion of anti-regime protests in recent days, signals an expanding campaign by President Bashar Assad aimed at crushing the country’s seven-week nationwide uprising.

Ammar Qurabi of the National Organization for Human Rights said the three women were protesting the siege and the cutting of power lines when they were shot dead by security forces or pro-government gunmen.

Qurabi said gunfire was continuing and several other people were wounded.

The events in Banias, a day after security forces killed 30 people in nationwide protests, came on the heels of a large-scale military operation in the flashpoint southern city of Daraa. The 11-day siege, in which about 50 residents were killed, triggered international outrage and condemnation.

The U.S. has already targeted three top Syrian officials as well as Syria’s intelligence agency and Iran’s Revolutionary Guard with sanctions over the crackdown. The European Union is expected to place sanctions on Syrian officials next week, and the U.N. said Saturday it is sending a team into Syria to investigate the situation.

An operation in Banias similar to the one in Daraa, where the uprising began, risks further isolating Assad’s regime, which has used brutal military force to crush the unprecedented revolt against his family’s 40-year dynasty.

Details of the troop deployment in Banias were scarce as phone lines and other communication were mostly cut off.