Libyan rebels and pro-Gaddafi forces exchanged heavy artillery fire near the western city of Zlitan on Friday as the rebels tried to push deeper into government-held territory east of the capital.
A Reuters team in Dafniya, on the outskirts of the rebels' western bastion of Misrata, described rebels firing artillery and rocket launchers with a range of about 20 km (miles). Rebels said they were aiming for tanks and munitions in Naimah near Zlitan.
"We had a strategy to finish everything today but some of the fighters think it's a game," a rebel unit commander called Mohammed Ali told Reuters. "They shot when they weren't supposed to shoot and they have ruined it," he said after rebels took cover at the main Dafniya front from a heavy mortar barrage.
Warplanes could be heard in the skies above, although it was unclear whether there had been air strikes.
Zlitan, just 160 km (100 miles) from Tripoli, is the next major town on the Mediterranean coast road to the capital. Capturing it would be a major victory.
In Misrata, rebel spokesman Ahmed Hassan said 10 civilians had been killed and another 40 wounded when Gaddafi forces shelled the city. The report could not be immediately verified.
The exchanges were the heaviest in the area since last week, when 31 rebels were killed.
At a field hospital in Dafniyah, ambulances arrived with at least five seriously wounded rebel fighters.
The rebels have said they will not attack Zlitan because of tribal sensitivities, but are recruiting fighters from the town and waiting for the residents to rise against Muammar Gaddafi.
NATO planes resumed bombardments of Tripoli on Friday with six loud explosions ringing out in the south of the city.
The rare daytime strikes, which hit the capital before noon, sent columns of thick black smoke into the sky.
A few hundred people filled the capital's Green Square waving green revolutionary flags and chanting pro-Gaddafi slogans following Friday prayers.
The rebellion erupted four months ago to the day in the eastern city of Benghazi. NATO intervention has been going on for nearly 13 weeks, longer than many of its backers expected, and strains are beginning to show within the alliance.
But French Military spokesman Thierry Burkhard suggested the rebels were homing in on Gaddafi's stronghold of Tripoli.
"The opposition forces seem to have taken the ascendancy on Gaddafi's troops, which shows just how much attrition they are enduring," he told reporters on Thursday.
The rebel advance, he said, was "essentially in the West and in a belt they are now developing around the Tripoli region."
Rebel advances toward Tripoli have been slow, while weeks of NATO strikes pounding Gaddafi's compound and other targets have failed to end his 41-year-old rule.
Rebel forces are fighting Gaddafi's troops on two other fronts: in the east of the country around the oil town of Brega and in the Western Mountains southwest of Tripoli.
Juma Ibrahim, a rebel spokesman in the Western Mountains town of Zintan, said Gaddafi loyalists were massing in Gharyan, about 120 km (90 miles) southwest of Tripoli.
"Battles continued today at the Tekot area (near Nalut) between pro-Gaddafi forces that used Grad missiles and tanks to shell the positions of rebels," he said, adding NATO strikes in the last 48 hours had been "very helpful."