Thousands of people are struggling to leave southern Lebanon, as Israel continues air strikes and ground raids.
Many fleeing civilians have been waving white flags
Israel issued a specific warning to civilians in 14 villages, telling them to leave by Saturday evening.
Later, the Israeli military said its forces had taken the village of Maroun al-Ras, thought to have been the launch site for rocket attacks against Israel.
The UN humanitarian chief is en route to Beirut, as the UN seeks to secure safe routes out for fleeing civilians.
The UN's Jan Egeland said half a million people needed assistance - and the number was likely to increase.
As concerns about hundreds of thousands of displaced civilians grew, Israel eased restrictions on Lebanon's blockaded ports to allow aid into the country.
Despite building up troops and tanks along the border, Israel has insisted it has no plans for a large-scale invasion.
The warnings issued to 14 villages came a day after Israel dropped leaflets warning Lebanese civilians to flee a broad swathe of the south.
The BBC's Martin Asser in the southern city of Tyre described long queues of taxis and cars negotiating bomb-cratered roads and making detours around destroyed bridges.
Many civilians from villages in the region had gathered in the city during the week and are now trying to leave. However, many people say they are reluctant to move without UN protection.
On the 11th day of fighting, Israeli jets knocked out TV and phone masts in the east and north of Lebanon, disrupting broadcasts for Hezbollah's Al-Manar television and the Lebanese Broadcasting Corporation.
Hezbollah continued to fire dozens of rockets into Israel, hitting the towns of Carmiel, Kiryat Shmona and Nahariya, and wounding several Israelis.
Israeli soldiers also continued ground incursions. The Israeli military said its forces had taken control of the village of Maroun al-Ras, and that they had eliminated what they described as major Hezbollah strongholds there.
There has been no independent confirmation.
Six Israeli soldiers have died in heavy fighting with Hezbollah militants in recent days.
Israel also briefly occupied the village of Marwahin, but has now withdrawn. The army has said limited raids across the border will continue, targeting Hezbollah bunkers and tunnels that cannot be destroyed from the air.
Correspondents say Israeli troops are likely to push deeper and more frequently into Lebanon over the coming days.
US Secretary of State Condoleezza Rice is travelling to the Middle East on Sunday, as is German Foreign Minister Frank Walter Steinmeier, who helped broker a prisoner exchange between Israel and Hezbollah in 2004.
In his weekly radio address, US President George Bush stressed the need for "confronting the terrorist group that launched the attacks and the nations that support it".
He described Syria as "a primary sponsor" of Hezbollah, and accused Damascus of helping provide the group with Iranian weapons.
His comments followed a report in the New York Times, citing US officials who said the US was rushing a delivery of satellite and laser-guided bombs to Israel.
The crisis was triggered by the capture of two Israeli soldiers by Hezbollah militants on 12 July.
Israeli government spokesman Avi Pazner told the BBC Israel was not interested in invading, conquering or occupying Lebanon, from where it withdraw troops in 2000.
"We only want to get rid of Hezbollah," he said.
Senior Lebanese officials have warned the country's army will go into battle if Israel invades.
More than 350 Lebanese have been killed in the 11 days of violence, many of them civilians.
Thirty-four Israelis have been killed, including 15 civilians killed by rockets fired by Hezbollah into Israel.