Mr Hur said the group's leader was arrested in the raid
More than 100 tanks have been seized from a militia group loyal to former Libyan leader Col Muammar Gaddafi, government officials say.
Nearly 30 rocket launchers were also captured when security forces raided a camp in Tarhuna, near Tripoli.
The officials say the Brigade of the Faithful group was behind last Sunday's car bombings which killed two people.
In a separate development, at least three people died in clashes between rival tribes in northern Libya.
A number of people were also reported to have been injured in the clashes in the town of Zlitan, south-east of the capital, Tripoli.
Libya remains awash with weapons left over from last year's uprising which ousted Col Gaddafi, and the new government has struggled to assert its authority across the vast country.
Militants escape
The capture of the tanks and other heavy weapons was announced by the authorities at a news conference on Thursday.
Interior Ministry spokesman Abdelmonem al-Hur said one person was killed and a number of others injured during Wednesday's raid on the camp Tarhuna, about 60km (35 miles) south-east of the capital.
In all, 13 people - including the group's leader - were arrested during the operation, but three militants managed to escape.
Mr Hur added that the authorities had believed the group "defended Libya and the revolution, but it turned out to be contrary".
Last Sunday, two people died and up to five were injured in the twin car bombings in Tripoli.
One blast took place near the former military academy for women, while the other struck close to the interior ministry.
The attacks took place as crowds prepared for mass morning prayers to mark Eid al-Fitr, the Muslim celebration at the end of the fasting month Ramadan.
