Pro-government forces in Libya have been accused by a human rights campaign group of using cluster bombs, which are banned by more than 100 countries.Human Rights Watch said one of its photographers saw three mortar-launched projectiles explode over a residential area of Misrata, in western Libya.
A government spokesman denied the allegation, calling for more evidence.
New attacks by government troops have been reported in Misrata, the only western city still in rebel hands.
One resident, Aous, told the BBC he had seen indiscriminate bombing and shooting from 0630 (0330 GMT) on Saturday.
"I listened to bombing and shooting everywhere. And I saw smoke going up just a few metres from my house.
"The shooting was random in this area - there are families here. They didn't make a difference between any houses, just shooting."
As well as cluster munitions there have been a number of reports that Libyan forces are using the Soviet-designed Grad rocket system in their bombardment of Misrata.
The Grad, which launches multiple rockets from mobile launchers, has been blamed for a number of civilian deaths in recent days, including eight people in a bread queue. Reuters news agency reported large numbers of Grads fired into Misrata on Saturday.
The BBC's Jon Leyne, in the eastern rebel stronghold of Benghazi, says the Grad is another indiscriminate weapon that - while not illegal - could be even deadlier than cluster bombs.
Launched from a truck containing up to 40 rocket pods and able to fire some 40 rockets in quick succession, Grads blanket a wide area and are said to have been used against the port of Misrata, a key link to the outside world for those in the city.
This is urban warfare of the nastiest kind, our correspondent says: on the one hand you have the rebels fighting the government and on the other government forces appear to be randomly shelling and using sniper fire in civilian areas.
There were also reports of renewed fighting near the eastern town of Ajdabiya, where rebels are regrouping on the road to the oil town of Brega.
'Appalling'
Releasing photographs of cluster munitions, New York-based Human Rights Watch said three projectiles had exploded over Misrata's el-Shawahda neighbourhood on Thursday night.
First discovered by a New York Times reporter and inspected by HRW researchers, the object photographed is said to be an MAT-120 120mm mortar projectile, which opens in mid-air and releases 21 "bomblets" over a wide area.
"Upon exploding on contact with an object, each submunition disintegrates into high-velocity fragments to attack people and releases a slug of molten metal to penetrate armoured vehicles," HRW noted.
HRW said the projectile it had examined had been manufactured in Spain in 2007, one year before Madrid signed the international Convention on Cluster Munitions.
Steve Goose, HRW's arms division director, said it was "appalling" that Libya was using such weapons, especially in a residential area.
"They pose a huge risk to civilians, both during attacks because of their indiscriminate nature and afterward because of the still-dangerous unexploded duds scattered about," he added.
HRW said it could not determine whether any civilians had been hurt by the cluster bombs which "appear to have landed about 300 metres [yards] from Misrata hospital".
The international Convention on Cluster Munitions, adopted in Dublin in 2008, prohibits its 108 signatories from using cluster weapons because of the threat they pose to civilians.
Libya is one of the states which has not signed the convention, along with countries such as the US, Israel, Russia and China.
Libyan government spokesman Moussa Ibrahim denied cluster bombs had been used in Misrata.
"I challenge them to prove it," he told reporters in the capital Tripoli.
Referring to inspections by humanitarian groups, he said: "To use these bombs, the evidence would remain for days and weeks, and we know the international community is coming en masse to our country soon. So we can't do this, we can't do anything that would incriminate us even if we were criminals."
There was no immediate comment from Spain, a signatory to the cluster munition convention, on the provenance of the bombs.
No reinforcements
Rebels in Misrata have been holding out against attacks for two months and UK Foreign Secretary William Hague has stressed that Nato needs to act swiftly to prevent a "massacre" in the city.
He said on Friday that Nato had been constrained by the need to avoid civilian casualties but had probably prevented the city from being overrun by Col Gaddafi's forces.
On Friday a meeting of Nato foreign ministers in Berlin ended without a commitment from non-participating nations to contribute combat aircraft to the alliance's military operations over Libya.
The US, UK and France said in a joint statement that the threat to Libyan civilians will not disappear while Colonel Muammar Gaddafi remains in power.
However, Russia has suggested Nato has been exceeding its UN Security Council mandate to protect civilians.
