At least 45 National Transitional Council (NTC) fighters have been killed and more than 200 wounded -- mostly by explosions or gunfire -- since they launched an offensive against Sirte last week, medics in Misrata said.
At least six explosions shook the town in the early afternoon as NATO aircraft overflew the town where forces loyal to Moamer Qadhafi battled NTC fighters seeking to oust them.
An AFP photographer said the attackers earlier were met by Grad rockets targeting their positions near the western bridge on the main highway into Sirte, five kilometres (three miles) from the city centre.
Despite the barrage of fire there were no casualties among the attacking forces who in turn unleashed Grad rockets on the defenders.
Qadhafi snipers were also focusing on NTC advancing forces.
On the eastern front, some six kilometres (nearly four miles) from Sirte, a sustained artillery and machinegun fire duel erupted in the early afternoon between Qadhafi troops and their foes.
The defending forces again showed stiff resistance against those trying to dislodge them.
"The offensive on Sirte has been high intensity in terms of casualties," Dr Suheib Abu Garza told AFP earlier in Misrata, about 150 kilometres (95 miles) east of Sirte, where the casualties of battle are being brought.
Garza said he had not seen such volumes of serious cases since Qadhafi loyalists laid siege to Misrata soon after the rebellion began in February.
NTC fighters moved in on Sirte, one of Qadhafi's final strongholds, from the west and south on September 15, while another NTC force is still fighting its way towards the city from the east.
Qadhafi's forces have put up unexpectedly fierce resistance and the NTC fighters have been forced to retreat from the city by night to allow NATO warplanes to target their weaponry.
At least three NTC fighters, all in their 30s, were killed in Sirte and 17 others were wounded in fighting on Tuesday, Misrata's general hospital, which centralises casualty figures, reported.
Sporadic rocket fire and mortar exchanges shook Sirte, witnesses said, although the former rebels say they have reduced their use of heavy artillery since Sunday in a bid to give families a chance to flee.
Meanwhile, 16 patients -- most in critical condition -- were evacuated on a Qatari military plane to Malta, easing the pressure on overwhelmed hospitals.
"There's too much pressure in the operating rooms so we are sending those in critical condition to operating theatres abroad," Dr Mahmud al-Bakhush told AFP.
Four of Misrata's CT scan machines were inoperative on Tuesday, complicating the assessment of trauma patients while intensive care units were so overwhelmed doctors were battling to cope.
"We've almost run out of ventilators," said Dr. Hakim Zakri.
NTC forces suspect Qadhafi enjoys a broad base of support in Sirte.
"The majority of residents are with Qadhafi," said Zuber al-Gadir, spokesman of the Misrata military council, adding he believed the loyalty stemmed from the fugitive leader's control over media.
Copyright AFP (Agence France-Presse), 2011