A human rights campaign group has accused pro-government forces in Libya of using cluster bombs, which are banned by more than 100 countries.
The New York based Human Rights Watch says one of its photographers had seen three of the bombs explode over a residential area of Misrata.
It said it could not determine whether any civilians had been hurt by the cluster bombs which "appear to have landed about 300 metres from Misrata hospital".
Researchers have been able to retrieve fragments of what they have identified as a Spanish made 120mm mortar projectile, which opens in mid-air and releases 21 sub-munitions over a wide area.
A doctor in Misrata told the BBC that's he's also seen cluster bombs being used by pro-Gaddafi forces.
Libya's government has denied the allegation.
United States president Barack Obama has acknowledged there is a stalemate on the ground in Libya, but says the noose is tightening on country's embattled leader, Muammar Gaddafi.
Mr Obama says he still expects the three-week-old air campaign to succeed in ousting Colonel Gaddafi.
Misrata medical staff overwhelmed
Medical staff in the besieged Libyan port of Misrata say they're overwhelmed by the number of casualties inflicted by forces loyal to leader Muammar Gaddafi.
The NATO allies have denounced what they call a "medieval siege" of Misrata, which is still being bombarded.
A BBC correspondent said staff at a hospital in Misrata were battling to treat civilians injured by mortars and rocket fire.
Government rockets crashed into the city on Friday, Reuters reports.
Residents told the television network Al Jazeera at least 120 rockets hit the city, where hundreds of civilians are reported to have died in a six-week siege.
Migrant ship leaves Misrata
Meanwhile, a ship with nearly 1,200 Asian and African migrants, many weak and dehydrated after weeks with little food or water, left Misrata on Friday for rebel-held Benghazi, an international aid agency said.
International Organisation for Migration (IOM) spokeswoman Jemini Pandya told Reuters that the migrants were all "very weak and dehydrated".
The agency said medical non-governmental organisations had set up a small hospital on the chartered Greek vessel Ionian Spirit, which had earlier unloaded 400 tonnes of aid supplies in Misrata.
In all, 1,182 migrants were aboard IOM's first mass evacuation vessel, due to arrive in Benghazi on Friday night.
The majority are migrants from Bangladesh and Egypt, but also included people from India, Iraq, Pakistan, Sudan and Eritrea.
They were among 8,300 migrants who have been living in the open around the port of Misrata without shelter, adequate food, access to clean water or medical care, according to the IOM.
Some have camped there since the crisis began two months ago.
An IOM official said they were the "forgotten victims" of the crisis.
