Faraj al-Swehli, commander of the Swehli Brigade, shows a document found on two British journalists arrested on suspicion of being spies, in Tripoli March 4, 2012.[Photo/Agencies]

TRIPOLI - Two British journalists working for Iran's Press TV who were detained late last month in Libya are suspected of being spies, the head of the militia which is holding them said on Sunday.

Faraj al-Swehli, commander of the Swehli brigade, said they had found among the journalists' possessions official Libyan documents, equipment used by the Israeli military and footage of them firing weapons.

"We believe they are spies," Swelhi said in Tripoli. He said it was too early to say what country they were spying for, but that this would be established by their investigation.

"After we have finished the investigation we are going to transfer them to the state authorities to pursue the legal process against them."

The two have been named as Nicholas Davies and Gareth Montgomery-Johnson. They were arrested on Feb. 22 in Misrata, about 200 km (130 miles) east of the capital. They are now being held in a Swehli brigade base in central Tripoli.

The commander, speaking at a news conference where he was flanked by subordinates in camouflage uniforms and sports shoes, said the two did not have Libyan entry visas in their passports.

He showed a grey plastic packet containing a field dressing with the words "Made in Israel," on it, which he said had been found on the two journalists. "These are used by the Israeli military," said Swehli.

He said the two had in their possession Libyan documents listing members of a Tripoli militia killed in a clash with a rival group late last year, and lists of sub-Saharan African mercenaries who fought alongside the forces of ousted leader Muammar Gaddafi.

Swehli showed the news conference footage he said had been recovered from the two Britons where they could be seen test-firing a gun.

Other footage appeared to show the journalists late at night in Tripoli's Algiers Square, dancing to Western pop music coming from a car's sound system.

Swehli said the two men were being well treated, and that they had been visited in detention by British consular officials and representatives from New York-based Human Rights Watch.

"I did not hit the prisoners and I am ready to stand before a court if there is any evidence against me," said Swehli.

A spokeswoman for Britain's foreign ministry, asked to comment on the spying accusations, said: "We are aware that two British nationals have been arrested in Libya. We are providing consular assistance."