Caretaker prime minister Najib Mikati said Tuesday his country was facing "one of the most dangerous phases of its history", urging the United Nations to provide aid for one million people displaced by Israeli air strikes.

"Around a million of our people have been displaced because of the devastating war that Israel is waging on Lebanon," the National News Agency reported Mikati as saying. "We urgently call for more aid to reinforce our ongoing efforts to provide basic support to displaced civilians," he added in a meeting with U.N. representatives.

The Israeli military said "intense fighting" was taking place Tuesday after it launched a ground offensive against Hezbollah in southern Lebanon and warned Lebanese residents not to travel by vehicle in the region.

"Intense fighting is taking place in southern Lebanon," wrote Avichay Adraee, a spokesman for the Israeli army, in a message published in Arabic on Telegram. "For your personal safety, we ask you not to travel by vehicles from the north to the south of the Litani River" in south Lebanon.

The Israeli military on Tuesday said it had begun a "limited, localized" operation against Hezbollah targets in southern Lebanon, opening a new front in its war against the Lebanese group.

In a brief announcement, it said it was striking Hezbollah targets in areas close to the Israeli border, and that air force and artillery units were carrying out attacks to support the ground forces. It gave no details on how long the operation would last, but said the army had been training and preparing for months.

Israel is "currently conducting" limited ground operations targeting Hezbollah inside Lebanon, the U.S. State Department said Monday.

"This is what they have informed us that they are currently conducting, which are limited operations targeting Hezbollah infrastructure near the border," State Department spokesman Matthew Miller told journalists.

A Bulgarian government jet has returned to Sofia with 89 nationals who were evacuated from Lebanon.

Prime Minister Dimitar Glavchev, who welcomed them at the Sofia Airport on Monday, said the government was discussing all options for future evacuations.

Lebanon's army is repositioning troops stationed on its southern border, a Lebanese military official told AFP Monday, after the US said Israel had informed it about limited ground operations inside Lebanon.

The Lebanese army is "repositioning and regrouping forces" at the southern border following threats of an Israeli incursion against Hezbollah targets, the official said, requesting anonymity to discuss sensitive matters.

The Israeli military declared a military zone in parts of its northern border with Lebanon on Monday ahead of possible ground operations.

"The areas of Metula, Misgav Am, and Kfar Giladi in northern Israel have been declared a closed military zone. Entry to this area is prohibited," the military said in a statement.

United Nations peacekeepers in Lebanon have been unable to conduct patrols because of the intensity of Israeli strikes and Hezbollah’s rockets targeting Israel, a U.N. spokesman said Monday.

"Our UNIFIL Blue Helmets remain in position in the mission’s area of responsibility, while the intensity of fighting is preventing their movements and ability to undertake their mandated tasks," Stephane Dujarric, spokesman for U.N. Secretary-General Antonio Guterres, told a media briefing.

Israel has informed the United States about limited ground operations targeting Hezbollah infrastructure inside Lebanon, the State Department said Monday.

"I've seen reports about ground operations. We've had some conversations with them about that; they have at this time told us that those are limited operations focused on Hezbollah infrastructure near the border," State Department spokesman Matthew Miller told journalists.

Parliament Speaker Nabih Berri confirmed Monday to Asharq Al-Awsat newspaper that Lebanon is still committed to what was agreed upon with American mediator Amos Hochstein regarding a path that leads to a ceasefire with Israel and the implementation of U.N. resolution 1701.

Berri said he had agreed on a ceasefire initiative with Hezbollah leader Sayyed Hassan Nasrallah, who was killed by an Israeli airstrike on Friday, and that the agreement is still "in effect."