Italian troops came ashore at Tyre in the first major reinforcement to the United Nations mission monitoring a ceasefire between Israel and Hezbollah.
Five inflatable dinghies each transporting seven soldiers arrived shortly before 7.30am (0430 GMT) on Saturday.
Lieutenant Federico Mariani, a spokesman for the Italian troops, said the soldiers would carry out a reconnaissance mission before the full contingent of 800 soldiers is transported ashore from five naval vessels anchored off the coast.
He said the soldiers would then begin deploying in the south.
The landing operation is expected to last all day. Two hundred more soldiers will go to Beirut on Sunday.
The five-ship Italian fleet set off for Lebanon on Tuesday carrying Italian marines and engineering corps specialists.
The arrival of Italian officers and soldiers, the largest new contingent since the August 11 security council resolution that halted the 34-day war, will bring to 3,180 the number of UN troops in south Lebanon.
Turkey and Indonesia have confirmed their willingness to send thousands of troops to join the United Nations Interim Force in Lebanon (Unifil).
An Italian Unifil helicopter drops
officers near a Tyre beach
The international force is being sent to Lebanon in an effort to prevent renewed fighting between Israel and Hezbollah.
Kofi Annan, the UN secretary-general, has also arrived in Iran on Friday where he says he will try to win Iranian support for the ceasefire in Lebanon.
Muslim nations offer troops
On Friday Turkey's government asked parliament to approve sending troops to Lebanon.
The ruling Justice and Development Party (AKP) also asked for parliament - which is currently in summer recess - to convene extraordinarily on September 5 to debate and vote on the motion.
The AKP holds an absolute majority in the 550-seat parliament, making it highly likely that the motion will be adopted.
Indonesia also said that it would probably send troops to Lebanon in October.
German spy chief in Beirut
Germany's spy chief has also arrived in Beirut on a mission cloaked in secrecy, amid speculation that Berlin aims to negotiate a prisoner swap between Israel and Hezbollah.
Ernst Urlau, accompanied by a five-member delegation, flew into Beirut's international airport amid tight security on Friday and was met by German ambassador to Lebanon Marius Haas.
A spokeswoman for German's Federal Intelligence Service (BND) declined to discuss the purpose of Urlau's visit, but denied reports he was serving as a go-between.
"The subject [of his talks] is not the prisoner exchange," she said.
In 2003, Germany mediated between Hezbollah and Israel to secure the release of a captured Israeli businessman in exchange for several hundred Lebanese prisoners.