TRIPOLI, Libya — Moammar Gadhafi's regime struck back at its opponents with a powerful attack Friday on the closest opposition-held city to Tripoli and a barrage of teargas and live ammunition to smother new protests in the capital. At least 37 people died in fighting and in an explosion at an ammunitions depot in Libya's rebellious east.
The bloodshed signaled an escalation in efforts by both sides to break the deadlock that has gripped Libya's 18-day upheaval, which has lasted longer than the Egyptian revolt that led to the ouster of President Hosni Mubarak and inspired a wave of protests across the region.
So far, Gadhafi has had little success in taking back territory, with several rebel cities repelling assaults and the entire eastern half of the country under rebel control. But the opposition forces have seemed unable to go on the offensive.
Meanwhile, in Tripoli — Gadhafi's most important bastion — his loyalists have waged a campaign of terror to ensure that protesters do not rise up in significant numbers.
Friday's assault on the rebel city of Zawiya, about 30 miles west of Tripoli, appeared to be the strongest yet by Gadhafi's forces after repeated earlier forays against it were beaten back.
In the morning, troops from the elite Khamis Brigade — named after the Gadhafi son who commands it — bombarded the city's western edges with mortar shells, heavy machine guns, tanks and anti-aircraft weapons, several residents said. By the evening, another brigade had opened a front on the eastern side. Armed Zawiya citizens backed by allied army units were fighting back.
The commander of the rebel forces — Col. Hussein Darbouk — was killed by fire from an anti-aircraft gun, said Alaa al-Zawi, an activist in the city. Darbouk was a colonel in Gadhafi's army who defected early in the uprising.
A witness in Zawiya's hospital said at least 18 people were killed and 120 wounded. Libyan state TV reported the attackers had retaken the city. But al-Zawi and other residents said it remained in rebel hands.
The Associated Press reported that a doctor on the scene said pro-Gadhafi fighters would not allow medics to treat the injured, opened fire on ambulances trying to assist and hauled away the bodies of some of the dead in an apparent effort to keep death toll reports low.
The doctor and other witnesses spoke on condition of anonymity for fear of retaliation.
The day's other fighting took place at Ras Lanouf, a small oil port 380 miles east of Tripoli, just outside the long swath of eastern Libya controlled by the opposition.
Rebels attacked Ras Lanouf on Friday afternoon, feeling flush with victory after repelling Gadhafi forces who attacked them days earlier at Brega, a larger oil facility just to the east. Fighters armed with Kalashnikovs and heavy machine guns were seen streaming in pickups from Brega heading in the direction of Ras Lanouf.
Ahmed al-Zwei, a member of the post-uprising town committee in nearby Ajdabiya, said the rebels were in control of the Ras Lanouf airstrip and the oil and gas facilities, and the regime forces had returned to their base at Sirte, a Gadhafi stronghold.
At least two dead and 16 wounded were taken to the hospital at nearby Ajdabiya, although that did not include the toll from other hospitals in the area. Al-Zwei, however, said the Gadhafi forces had killed 20 guards from the two facilities.
To the northeast, hospital officials said at least 17 people were killed in an explosion at an ammunition storage facility at a military base about 20 miles from the rebel stronghold of Benghazi. The cause of the blast was unclear.
The fall of other parts of the country has made control of Tripoli crucial for Gahdafi. His loyalists have taken fierce action to ensure protesters cannot rise up and overwhelm the city.
Some 400 protesters marched out of the Murad Agha mosque after noon prayers in the eastern Tripoli district of Tajoura.
Pro-Gadhafi forces quickly moved in. They fired volleys of tear gas and — when the marchers continued — opened fire with live ammunition.