Reports say at least 30 people are dead after forces loyal to Libyan leader Muammar Qaddafi launched a massive attack to regain control of the opposition-controlled town of Zawiya, 50 kilometers west of the capital, Tripoli.
Among the dead was the rebels' top commander, a former army colonel who defected to join the forces trying to oust the North African strongman, who has ruled for four decades and has vowed to remain in power despite an 18-day-old national uprising against his regime.
The Associated Press reported that Colonel Hussein Darbouk was shot to death by fire from an anti-aircraft gun, quoting a local activist named Alaa al-Zawi.
Reuters news agency, quoting local residents, has reported that at least 30 people have been killed in Zawiya clashes.
The assault on the Zawiya, which appeared to be the strongest offensive yet by Qaddafi's forces, began in the morning, when an elite brigade used mortars, heavy machine guns, tanks, and aircraft to attack people as they left noon prayers.
Armed citizens backed by allied army units fought back, and a witness who was at Zawiya's hospital said at least 18 people in the city had been killed and 120 wounded.
By day's end it was not clear whether the city remained in rebel hands. Libyan state TV claimed the attackers had retaken the city. But witnesses said it remained in opposition hands, with skirmishes continuing after nightfall.
Meanwhile, Internet service in Libya appeared to have been completely cut amid the violence. U.S.-based Arbor Networks, which monitors Internet use, said Internet traffic coming in and out of Libya had ceased from late in the day on March 3. Google, which tracks the usage of its sites, also said that its sites had apparently been unavailable in Libya from around the same time.
In the east, rebels advanced on an oil port along the Mediterranean coast in their first offensive against government forces. Explosions were heard as the two sides battled around the air strip at Ras Lanouf, a small oil port 620 kilometers east of Tripoli, and reports said at least two people were killed.
The fighting underscored how both sides are trying to break the stalemate that the upheaval has created. With rebels in control of the eastern half of the country, they have started to move westward, advancing toward the capital.
On March 3, U.S. President Barack Obama made his strongest comments to date on the upheaval and expressed concern that a stalemate could mean Libya is descending into a long, bloody civil war.
"There is a danger of a stalemate that, over time, could be bloody. And that is something we are obviously considering. So what I want to make sure of is that the United States has full capacity to act potentially rapidly if the situation deteriorated in such a way that you had a humanitarian crisis on our hands," he said.
Terror In Tripoli
Meanhile in Tripoli, security forces fired guns and tear gas to disperse antigovernment protesters -- the first opposition demonstrations in the Libyan capital since a violent crackdown by government troops a week ago.
The demonstrators began their protests in the eastern part of Tripoli after Friday prayers. Libyan authorities blocked foreign journalists from leaving their hotel to report on the protests in the capital.
Qaddafi has previously denied that any Libyans have been involved in antiregime demonstrations and challenged foreign journalists to show him one demonstration by Libyans against his regime. Qaddafi claims the uprising in Libya is inspired by Al-Qaeda terrorists and is being carried out by youths who are "stoned on drugs."
A Libyan government spokesman said about 130 journalists were being kept at the Rixos hotel because their presence could trigger violence from what he described as "affiliates of Al-Qaeda."
Correspondents at the Rixos hotel report hearing gunshots outside overnight. But Qaddafi's spokesman dismissed the reports as an attempt by Al-Qaeda terrorists to disturb stability in central Tripoli.
Elsewhere in the capital, residents of two working-class neighborhoods where anti-Qaddafi protests took place a week ago say they are under constant surveillance by pro-Qaddafi fighters.
Several people in the neighborhoods of Feshloom and Tajura -- speaking on condition of anonymity because they fear reprisals by Libya's secret police -- said militias loyal to Qaddafi have been using photographs taken at last week's protest to track down young men involved.
Residents attribute the disappearances of young men from their neighborhoods to arrests by Libya's secret police.
Signs Of Resistance
On Libya's north-western border with Tunisia, where an estimated 100,000 people have fled in the past two weeks, the UN refugee agency says pro-regime forces are now manning the Libyan side.
Melissa Fleming, spokeswoman for the UN High Commissioner for Refugees, said that the flow of people crossing the border had slowed and that the agency was concerned people were being prevented from making it across.
Washington has continued to call for Qaddafi's immediate resignation, and today State Department spokesman Philip Crowley said "the people of Libya win ... with Qaddafi's departure."
"We are gravely concerned about the ongoing violence and obviously, there is a risk that this violence could deepen into something like a civil war. We want to do everything that we can to avoid that happening, and again, the best solution here is for Colonel Qaddafi to give up the fight, step aside, and open the door for new leadership in Libya," he said.
Qaddafi's government has taken foreign journalists on a tour of western Libya as part of an effort to show that Qaddafi remains in control there.
Correspondents say towns and villages erupted in jubilation as their convoy passed through -- with crowds of supporters shouting "God, Muammar, Libya, together."
But signs of resistance were apparent. In several towns, buildings had been torched and many house fronts have been covered with antigovernment slogans. Roads in areas under Qaddafi's control have been heavily fortified with army tanks, anti-aircraft guns, and truck-mounted rocket launchers.
Written by Ron Synovitz with agency reports.