* Arms site in southern Lebanon blew up last week

* U.N. peacekeeping chief: arms were old but in good order

* Some 'civilians' confronting U.N. troops were Hezbollah

* Hezbollah denies breaching U.N. resolution (Adds U.N. diplomats in paragraph 4)

By Louis Charbonneau

UNITED NATIONS, July 24 (Reuters) - The U.N. peacekeeping chief has said there are signs an illegal weapons stockpile that exploded last week in southern Lebanon belonged to the Lebanese guerrilla movement Hezbollah.

In a speech delivered behind closed doors to the Security Council on Thursday, U.N. peacekeeping chief Alain Le Roy also said that some of the people who tried to prevent U.N. peacekeepers in Lebanon (UNIFIL) from investigating the site were Hezbollah members dressed in civilian clothes.

"A number of indications suggest that the depot belonged to Hezbollah, and, in contrast to previous discoveries by UNIFIL and the Lebanese Armed Forces of weapons and ammunition, that it was not abandoned but, rather, actively maintained," he told the 15-nation council in the speech, obtained by Reuters.

Le Roy said the mere presence of such arms south of the Litani River represented a "serious violation of resolution 1701." U.N. diplomats told Reuters it was the first time the world body has criticized Hezbollah so directly and sharply.

Security Council resolution 1701, which ended the 34-day war in 2006 between Israel and Hezbollah, banned all unauthorized weapons between the Litani River and the Blue Line, the U.N.-monitored border between Israel and Lebanon.

Hezbollah is backed by Iran and Syria.

The weapons at the site of the explosion were from various countries and included mortars, AK-47s, artillery shells and 122mm rockets, Le Roy said.

ARMS IN 'GOOD ORDER'

"The weapons and ammunition dated from the 1970s to the 1990s and generally appeared to be in good order," he added.

After Le Roy's speech, U.S. Deputy Ambassador Alejandro Wolff joined Israel in accusing Hezbollah of violating the U.N. weapons embargo in southern Lebanon and undermining the efforts of U.N. peacekeepers there.

UNIFIL said last week that peacekeepers had been pelted with stones by a crowd of about 100 Lebanese in the village of Khirbet Selim while trying to investigate the July 14 explosion at the suspected arms dump. Le Roy said the blast site was still being investigated.

A Hezbollah parliamentarian denied on Friday the movement had any role in the disturbances and said it was keen to restore relations between UNIFIL and local people to normal.

"The baseless American accusations are a repetition of the Israeli position and an expression of the U.S. administration's support for continuous Israeli aggression against Lebanon via its violations and spy networks," Hassan Fadlallah told Reuters.

He denied the blast was a violation of resolution 1701, saying it was a one-off accident that involved the explosion of an arms cache that had been in place before the 2006 war.

Fadlallah said the U.N. Security Council had done nothing to stop Israeli violations of Lebanese sovereignty, including almost daily military flights in breach of 1701. U.N. officials have repeatedly urged Israel to halt such illegal overflights.

Israel's U.N. ambassador, Gabriela Shalev, said in a letter to the Security Council that the arms cache that exploded clearly belonged to Hezbollah.

She said the actions of Hezbollah represented "a clear violation of 1701 which gravely endanger the stability in the region ... (and) the local Lebanese population." (Additional reporting by Laila Bassam in Beirut; editing by Mark Trevelyan)

AlertNet news is provided by