Prime Minister Fuad Saniora's office also said the government asked U.N. peacekeepers in southern Lebanon to help repatriate two suspected spies it believes fled across the heavily fortified border to Israel earlier this week.

Lebanese authorities have arrested 15 people in recent weeks on allegations of spying for Israel on the militant group Hezbollah, which fought a monthlong war with the Jewish state in 2006. Authorities found sophisticated survey and transmission equipment in the possession of some of the suspects, officials have said.

The latest round of arrests was one of the biggest in the long-running espionage war between the two countries. If convicted, those arrested could face the death penalty.

Israel's government routinely refuses to discuss its intelligence activities. But the Shin Bet security agency this week warned Israelis to be careful when using social networking sites such as Facebook, contending Arab groups are using them to recruit and hire spies.

In one instance, Israeli intelligence said an Israeli Facebook user was contacted by a man who introduced himself as a Lebanese agent and offered money for information.

The Lebanese complaint was filed by the country's U.N. mission Wednesday. Speaking to reporters the same day, Saniora said the alleged spying activities were "an aggression against the sovereignty of Lebanon."

Saniora also said it was a "blatant and glaring violation" of U.N. Security Council Resolution 1701, which ended the 2006 war between Israel and Hezbollah that killed more than 1,200 people in Lebanon and about 160 in Israel.

Spying allegations in Lebanon are particularly serious because Hezbollah fought the Israeli army on its territory and the two sides continue to trade accusations and threats. Hezbollah, although a heavily armed guerrilla movement, has a major political arm and enjoys the support of the government.

The suspected spies arrested by Lebanon include 13 Lebanese and two Palestinian refugees. One of them is a former security general and two others were members of the Lebanese security forces.