"Yesterday it was a disaster," Dr Sarahat Atta-Alah told Reuters at Ajdabiya hospital in eastern Libya on Wednesday.
Rebels have said they have encircled Brega, which they must take if they are to advance towards Tripoli, but fighters said they were still coming under fire from pro-Gaddafi forces.
Brega, which provides access to most of Libya's eastern oil network, has changed hands several times in five months of fighting along Libya's Mediterranean coast.
Rebels said on Tuesday they had encircled the town, which if captured would mark a major boost for their campaign to oust Gaddafi. Insurgents said they were dug in to the south and east of Brega and in control of its eastern residential sector.
The Libyan government has denied the rebels' reports, saying its soldiers are in Brega.
Doctors at the hospital in Ajdabiya, which lies to the east of Brega, said they expected more fighting later on Wednesday.
A rebel lieutenant, who gave his name as Ihab, said rebel forces were between 5 and 10 km (3 and 6 miles) outside Brega and Gaddafi's forces were still in the city.
He said the area was littered with mines and Gaddafi's forces had filled trenches with gasoline, which could be set on fire if rebels approached.
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