BEIRUT, Lebanon – Israeli troops sealed off a Hezbollah stronghold Tuesday and widened their foothold in southern Lebanon, but officials said Israeli bombs killed six people in a south Lebanon town and two U.N. observers in a border outpost with two other peacekeepers feared dead.

Two weeks into the war, a senior Hezbollah leader said the guerrillas had not expected such an Israeli onslaught when they snatched two Israeli soldiers July 12.

U.N. Secretary General Kofi Annan said the strike on a clearly marked U.N. border outpost was “apparently deliberate” and demanded Israel investigate.

A bomb dropped by an Israel warplane scored a direct hit on the post in the town of Khiyam, near the eastern sector of the border, U.N. officials said.

The victims were from Austria, Canada, China and Finland, U.N. and Lebanese military officials said. It was not immediately known which two were confirmed dead.

Israel’s U.N. Ambassador Dan Gillerman expressed his “deep regret” for the deaths and denied Isarel hit the post intentionally.

“I am shocked and deeply distressed by the hasty statement of the secretary-general, insinuating that Israel has deliberately targeted the U.N. post,” he said, calling the assertions “premature and erroneous.”

Israeli commanders said they would not push deep into Lebanon but were determined to stop Hezbollah missiles that have continued despite Israel’s punishing raids on Hezbollah targets.

A new volley of Hezbollah rockets hit northern Israel, killing a teenage girl. Hezbollah’s leader, Sheik Hassan Nasrallah, issued a taped television message saying guerrillas would now start firing rockets deeper into Israel.

Tuesday marked a month since the start of what is now a two-front war between Israel and Islamic militants.

On June 25, an Israeli soldier was captured by Hamas militants in Gaza, prompting an Israeli offensive there. Two weeks into that flare-up, Hezbollah snatched the two other soldiers.

In that month, the crisis has spiraled far beyond anyone’s imagining.

Mahmoud Komati, the deputy chief of the Hezbollah politburo, told The Associated Press that the guerrilla’s leadership had not expected a massive offensive when it snatched the two Israeli soldiers.

“The truth is – let me say this clearly – we didn’t even expect (this) response … that (Israel) would exploit this operation for this big war against us,” he said.

Instead, he said Hezbollah had thought Israel would respond to the soldiers’ capture by snatching Hezbollah leaders in commando raids and that negotiations for a swap would start, giving Hezbollah the chance to try to win the release of Lebanese prisoners held by Israel.

He called the Israeli assault “unjustified” and said Hezbollah would not lay down its weapons.

Israel and the United States say their ultimate aim is to reshape Lebanon to end Hezbollah’s presence by the border, strengthen democracy in the country and ensure lasting peace with Israel.

In the process, Lebanon has been ravaged, with hundreds killed, nearly a half-million driven from their homes and vast damage to roads.