NEW YORK (

TheStreet

) -- Libyan Foreign Minister Moussa Koussa resigned on Thursday, the British government said, as troops loyal to embattled leader Moammar Gadhafi continued to pummel the rebel opposition, according to reports.

Pickup Trucks of War: In Photos

As one of the autocrat's closest confidants, Koussa is likely privy to inside information. However, Britain said it refused to offer him immunity from prosecution in return for his possible intelligence about Gadhafi's military plans,

The Associated Press

reported.

Koussa's resignation is being interpreted by some as a sign of weakness in Gadhafi's reign. Tommy Vietor, U.S. National Security Council spokesman, said that his defection "demonstrates that the people around Gadhafi understand his regime is in disarray."

Gadhafi refuses to admit that Koussa has resigned and instead claims that it was a personal decision driven by health problems.

A second top Libyan official, Ali Abdussalam el-Treki, defected Thursday to Egypt,

AP

reported, in another sign of the Libyan government may be weakening.

"We believe that the regime is crumbling from within,"

AP

quoted opposition spokesman Mustafa Gheriani as saying in Benghazi, the rebels' de facto capital. "We hope the defections continue and I think he'll find himself with no one around him."

Despite the aid of Western air strikes, Gadhafi's troops have forced the rebels to retreat. The government army used superior arms to take back most of the territory along the eastern coast from the opposition.

U.S. officials revealed Wednesday that President Barack Obama had authorized covert operations,

Reuters

reported. The CIA has sent small teams of operatives to join the rebels in Libya while the U.S. considers whether to arm the opposition. White House press secretary Jay Carney said that no decision has been made yet, while U.S. Defense Secretary Robert Gates vowed that Obama wouldn't send ground troops into Libya.

Libyan rebels prepare heavy machine guns during an exchange of fire with Gadhafi's forces along the frontline outside Brega, Libya on Thursday, March 31.

"I can't speak to any CIA activities but I will tell you that the president has been quite clear that in terms of the United States military there will be no boots on the ground," Gates said,

Reuters

reported.

The opposition has been trying to move west across Libya in an attempt to retake all the main oil terminals lost to pro-Gadhafi forces, but the government troops continue to crack down, firing Grad rockets, artillery shells and live ammunition.

The

rebel fighters have been attempting to fight back using their own truck-mounted rocket launchers

, but are being met with a fierce bombardment, forcing them to flee,

Reuters

reported, citing rebel witnesses.

Rebels were slammed with heavy shelling from Gadhafi's forces when they tried to advance on Brega on Thursday.

"There were loads of

rebels wounded at the front lines this morning," rebel fighter Fathi Muktar said,

AP

reported.

Fierce clashes were also reported in Misrata, where rebels said Gadhafi's forces had killed 38 civilians in the past two days alone.

"Massacres are taking place in Misrata," rebel spokesman Sami told

Reuters

by telephone.

The death toll from the unrest in Libya is believed to be as high as 1,000, the British government said.

--

Written by Theresa McCabe in Boston

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