Rebel officials say Libyan leader Moammar Gadhafi's forces have laid vast quantities of mines and other explosive devices around the strategic port of Brega, slowing efforts to seize the town and enabling loyalist troops to sabotage key oil facilities.

An opposition military spokesman said Thursday that an estimated 400,000 mines had been planted in and around Brega. He said the mostly volunteer rebel force is working to clear them with almost no help from experts.

Mr. Gadhafi's troops have used a number of methods to push back the rebel advance on the city, including filling trenches with fuel and setting them on fire.

Mahmoud Jibril, the rebel's diplomatic chief, said government forces have boobytrapped Brega's oil fields so they can be blown up if they lose control of the town. Jibril said Brega “is a big minefield right now” and that “even some oil establishments, some oil fields, full of explosives.”

Meanwhile, the rebels said they have captured a key government commander in fighting near the western town of Zlitan. Opposition leaders said General Abdul Nabih Zayid was caught late Wednesday after advancing fighters overran his command post on the outskirts of Zlitan.

In a separate development, Mr. Gadhafi ruled out negotiations with the rebels trying to end his decades-long rule. In an audio message delivered Thursday to a crowd of thousands of supporters in his hometown of Sirte, the Libyan leader said “there will be no talks between me and them until Judgment Day.”

In a separate speech broadcast on Libyan television, Mr. Gadhafi urged families and tribal leaders from Misrata to retake Libya's third-largest city from rebels who have pushed his troops away after four months of bitter fighting.

Earlier, rebel leaders visiting France asked President Nicolas Sarkozy for military aid to enable them to march on Tripoli, Mr. Gadhafi's stronghold.

The rebel delegation made the request in Paris during a meeting on Wednesday. Afterward, a representative from Misrata said the rebels believe they can march on the Libyan capital within “days” with “a bit of help” from friends such as France.

French writer and rebel supporter Bernard-Henri Levy also attended the talks. He said the rebels told Mr. Sarkozy they can seize Tripoli by attacking from Misrata to the east and from rebel-held mountainous territory to the south of the capital.

It is not clear how the French president reacted to the rebel appeal. France previously dropped arms to rebels in Libya's western mountains last month.

France is participating in a three-month-old NATO-led campaign of airstrikes on pro-Gadhafi forces. The airstrikes support rebels who began an uprising in March to end Mr. Gadhafi's 42-year autocratic rule.