An Israeli army spokesman confirmed that a warship was hit by a rocket, but said that there were no major damages or casualties.
The attack on the warship on Friday was carried out by a remote-controlled drone, which indicates that Hezbollah has added a new weapon to the arsenal of rockets and mortars it had been using against the Israeli army.
Hezbollah-run Al-Manar TV reported earlier that the Lebanese resistance movement has attacked an Israeli warship that had been firing missiles into south Beirut.
"Now in the middle of the sea, facing Beirut, the Israeli warship that has attacked the infrastructure, people's homes and civilians - look at it burning," Hezbollah's leader Sheikh Hassan Nasrallah said.
Israeli Prime Minister Ehud Olmert has vowed to continue the military operations in Lebanon until Hezbollah was neutralized. Senior Israeli officials also threatened to assassinate Sheikh Nasrallah.
Israel's Interior Minister Roni Bar-On warned on Thursday that Nasrallah "decided his own fate."
"We will settle our accounts with him when the time comes," he said.
- "Open war"
The latest Israeli air strike came as the Jewish state stepped up its terror raids on Lebanon to pressure Hezbollah, whose fighters kidnapped two Israeli soldiers on Wednesday in a cross-border raid, which also left eight Israeli troops dead.
According to the Associated Press news agency, the fresh Israeli strikes brought the Lebanese death toll to more than 73 civilians.
Correspondents suggest that the speech, which didn't mention the latest missile attack on Nasrallah's offices, was prerecorded.
Sheikh Nasrallah has earlier said that the captured Israeli soldiers will only be returned through "indirect negotiations and an exchange of prisoners", and warned that any invasion of Lebanese territory would be met by force.
- Relentless attacks
Israel pounded residential buildings, roads, bridges, power plants, communication networks and bombed Beirut's international airport for the second day Friday, Reuters news agency reported.
Witnesses said Israeli warplanes pounded Hezbollah's command headquarters in Beirut's Shia-dominant southern suburbs, killing more than three civilians and wounding 40 others.
Israel also bombed the Jiyyeh power plant south of Beirut, and a base for Palestinian resistance fighters in eastern Lebanon, security officials said, adding that Israeli warplanes fired at least two missiles at Beirut's international airport, which has been shut since Israel bombed its runways on Thursday.
In overnight raids, Israeli aircrafts bombed the main Beirut-Damascus highway, tightening an air, sea and land blockade of Lebanon.
Fearing more Israeli attacks, thousands of tourists, mostly Gulf Arab nationals, fled Lebanon to neighboring Syria, now the country's only gateway to the outside world.
The crisis also raised world oil prices to record highs and shook financial markets in Israel and Lebanon.
Correspondents say many areas in southern Lebanon are now without power. Lebanese citizens also queued for petrol and hoarded food and drink. Power rationing started and many stores and offices remained shut.
"It's a massacre," said Abu Talal, a 48-year-old Lebanese citizen who attended the funeral of Shia cleric Sheik Adel Akkash, who was killed Thursday by an Israeli air strike along with his wife and eight children, ages 3 months to 15 years.
"This is the (Israeli) arrogance. The raids aim to terrorize us, but morale is high."
Meanwhile, Hezbollah, which vowed to avenge the "massacres" of Lebanese by Israel, continued firing rockets into Israel. Reports say at least 70 missiles were fired on northern Israel throughout the day. Four Israelis have been killed in such attacks over the past two days.
On Thursday, one rocket hit Haifa, Israel's third-largest city, an attack described by Israel as a "major escalation" of the crisis. However, Hezbollah denied that it was involved in the Haifa attack.
- "Regional war"
The Israeli offensive has sparked international condemnation, with the European Union and Russia strongly denouncing Israel's "disproportionate use of force".
The UN chief Kofi Annan's personal representative to Lebanon, Gier Pederson, also said he was "highly alarmed by Israel's heavy attacks and escalation" while Palestinian President Mahmoud Abbas warned of the risk of a "regional war".
Envoys from the United Nations and the European Union are being dispatched to the region to try to defuse the crisis, while the Security Council is to meet on Friday and Arab Foreign Ministers on Saturday.
The Middle East "quartet" - the European Union, Russia, the United Nations and the United States – said that it's holding "active consultations in order to work out recommendations for resolving the situation."
Some Israeli analysts warned that Syria could be Israel's next target.
The U.S. President George W. Bush, who recognized Israel's right to defend itself without criticizing Israel's terror raids on Lebanon, also said that Syria's President Bashar al-Assad, who withdrew all his troops from Lebanon last year, should be held responsible for the escalation of violence.
Syria's ambassador to the United States also said that Washington should use its power to restrain Israel and push for renewed peace talks.