Two Lebanese men suspected of spying for Israel fled across the heavily fortified border to the Jewish state Monday, the second such escape since Lebanon stepped up a campaign of arrests against those thought to be working for its archenemy, said officials.

Authorities arrested two other Lebanese men over the weekend on suspicion of collaborating with Israel, raising the total number of suspected spies arrested in the past few weeks to 15, said security officials.

Lebanon considers itself at war with Israel and spying for or collaborating with the neighboring country can be punishable by death.

The arrests, mainly in southern Lebanon, appear to have targeted those suspected of gathering information about Hezbollah militants for Israel's Mossad intelligence agency. The Iranian-backed Hezbollah guerrillas fought a 34-day war with Israel in 2006 that killed 1,200 people in Lebanon and 159 in Israel.

The two men who escaped to Israel on Monday crossed the border near the village of Yaroun with their children, said a senior military official. A man wanted by authorities escaped in a similar manner on May 5, according to a top security official.

It was unclear how they managed get past the border fence without triggering the electronic alarms that have alerted Israelis to similar crossings in the past. Lebanese citizens who try to sneak into Israel are normally detained, questioned and sent back to Lebanon.

There was no immediate word from Israel, which has declined to comment on the recent espionage allegations.

The weekend arrests took place in southern Lebanon and the eastern Bekaa Valley, said the security officials. They said suspicious transmission devices were seized in related raids.

The officials all spoke on condition of anonymity because they were not authorized to talk to the media.

Nine of the 15 people arrested in recent weeks have been charged with collaborating with Israel. They include a retired general, his wife and his nephew, a government security agent.

Hezbollah leader Sheik Hassan Nasrallah said in a televised speech later Monday that his guerrillas will be on high alert during upcoming Israeli military maneuvers.

Nasrallah said the five-day maneuvers will begin on May 31, but Israeli defense officials said Friday that no date has been set yet for the joint U.S-Israeli war games that occur every two years and are dubbed "Jennifer Cobra." The Israeli officials, who spoke on condition of anonymity because they were not authorized to talk to the media, said the exercises include testing anti-missile systems.

"We don't believe that the Zionist enemy will launch a war" against Lebanon, said Nasrallah, whose group is known to posses thousands of rockets in southern Lebanon. "But we will be present, ready and awake."