San Francisco -- An international group of hackers threatened Saturday to wage a cyberwar against BART in retaliation for the agency's decision to cut cell phone service to prevent a separate protest last week.

The activist group, known as Anonymous, also called for a nonviolent protest Monday evening at BART's Civic Center Station.

Members of the Anonymous group have claimed responsibility for disrupting Tunisian and Libyan government websites to coincide with street protests.

BART's shutdown of service was condemned by some free-speech advocates who said the transit officials, fearing that organizers used phones to coordinate their movements, had denied the protesters' rights to peacefully gather.

"In the Bay Area, we've seen people gagged, and once more, Anonymous will attempt to show those engaging in the censorship what it feels like to be silenced," a news release from the group said.

The group also encouraged Monday's protesters to carry video cameras, "to record further abuses of power by the police and to legitimize the protest. The media will certainly spin this in an attempt to make our actions appear to be violent or somehow harmful to the citizenry at large."

BART aware of plans

Jim Allison, a BART spokesman, said officials are aware of the planned protest and have held meetings to prepare for the event.

He would not say whether officials would turn off cell service again.

"The safety of our customers is our No. 1 priority, and we're going to do what we can to keep people safe," Allison said. "We're just going to leave it at that."

On Thursday, BART switched off the transit system's underground cell phone network in downtown San Francisco after it learned that individuals were planning to use mobile devices to coordinate a protest. The people were protesting a July 3 fatal shooting by BART police.

Some of BART's critics compared the shutdown to the Egyptian government's blocking of Internet and cell phone service during protests this spring.

State Sen. Leland Yee, D-San Francisco, was one of those who slammed BART's action.

"I am shocked that BART thinks they can use authoritarian control tactics," Yee said in a statement Saturday. "BART's decision was not only a gross violation of free speech rights; it was irresponsible and compromised public safety."

Protesters to wear red

In its release, Anonymous said that members at Monday's 5 p.m. demonstration would wear red, a symbolic color.

"We will be wearing 'blood' stained shirts for remembrance to the blood that is on the hands of the BART police," the group said in its announcement.