Four Canadian warplanes have again bombed a Libyan ammunition dump south of the embattled city of Misrata.  

The second raid on the target, initially hit on Sunday, was ordered during the last 24 hours after surveillance images showed some bunkers survived the first attack.

Lt.-Col. Chris Lemay, a spokesman for the Ottawa-based Canadian Forces Expeditionary Command, said the CF-18s completed their mission and returned to base in Trapani, Italy, without incident.  

He had no information on casualties on the ground.  

The Canadian strike took place amid some of the heaviest bombardment of the air war as an American ship in the Mediterranean unleashed a barrage of cruise missiles at Libyan missile storage facilities in the Tripoli area.

The USS Barry, a guided missile destroyer, launched 22 Tomahawk cruise missiles at weapon storage sites around Tripoli on Tuesday, according to a U.S. defence official.

It also came as a Libyan gunboat fired on merchant ships in the waters off Misrata. A U.S. P-3C Orion patrol plane was in the vicinity and fired missiles at the patrol ship, forcing the 12-metre vessel to run aground.  

An American A-10 Thunderbolt, normally used against tanks, also attacked two Libyan ships near Misrata, which has been under siege by forces loyal to dictator Moammar Gadhafi.

One vessel was destroyed while the other was abandoned, said a NATO coalition statement.  

The attacks on the ships were justified as being in defence of civilians. Critics are becoming more alarmed at the scope of the bombings and Russia's envoy to NATO said the coalition had exceeded its mandate.

Canadian CP-140 patrols coast 

Lemay said a Canadian CP-140 aircraft flew a long-range patrol of the Libyan coastline on Tuesday, but encountered no resistance. Unlike the American P-3s, the Canadian Auroras are not equipped with missiles.  

If they were fired on, they'd have to take evasive action and call for help.  

Misrata is fast becoming a major focus for Gadhafi's troops and over the last few days they threw more tanks and troops at the rebel-held town, the country's third-largest community.  

As many as 140 civilians have been reported killed in fierce fighting. There are reports of random artillery barrages on civilian populated areas.  

Senior world diplomats, meeting at crisis talks in London, pointed to the slaughter in Misrata as proof Gadhafi must go, but the official position of the coalition nations remains that regime change is not their goal.  

Gadhafi's forces have kept their tanks close to residential neighbourhoods and hospitals in Misrata, a tactic that's kept NATO warplanes away for fear of civilian casualties.

Gadhafi forces rout rebels from Bin Jawwad 

Meanwhile, rebels who had advanced toward the Gadhafi stronghold of Sirte were hammered with tanks and rockets on Tuesday, prompting a panicked retreat in an hours-long battle.

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Rebel fighters run under machine-gun fire and mortars after forces loyal to Gadhafi attacked them near Bin Jawad in eastern Libya, Tuesday. (Finbarr O'Reilly/Reuters)

Opposition fighters pleaded for supporting airstrikes as they fled the hamlet of Bin Jawwad amid crashing artillery. No such strikes were launched during the fighting, and some rebels shouted, "Sarkozy, where are you?" — a reference to French President Nicolas Sarkozy, one of the strongest supporters of using air power against Gadhafi.

Some loyalist forces pursued the retreating rebels to the outskirts of Ras Lanouf, where the thud of heavy weapons was heard and black smoke rose from buildings.  

"If they keep shelling like this, we'll need airstrikes," said Mohammed Bujildein, a 27-year-old rebel fighter. He was gnawing on a loaf of bread in a pickup truck with a mounted anti-aircraft gun, waiting to fill up from an abandoned gas tanker truck on the eastern side of Ras Lanouf.  

With international strikes, he boasted, "we'll be in Sirte tomorrow evening."

"This today is a loss, but hopefully we'll get it back," he said.

In the more densely inhabited western half of Libya, Gadhafi has largely crushed the rebellion in Tripoli and in several towns that rose up against his rule since the turmoil began Feb. 15. Other towns and cities in the west never generated an effective anti-Gadhafi uprising.

With files from The Associated Press