Addressing a meeting of Arab finance ministers on Tuesday, Siniora called for Arab funds to enable Lebanon to recover from the 34-day Israeli offensive in July and August.
"The Lebanese have paid a heavy price in lives and properties as a result of this devastating war. Also, nearly a quarter of Lebanon's population was displaced from their homes during the [Israeli] aggression," Siniora told the Arab League's economic and social council.
"Direct and indirect economic losses reached billions of dollars."
Lebanon says it needs about $3.5 billion to repair buildings and infrastructure damaged in the Israeli offensive.
Saudi Arabia's King Abdullah has pledged $500 million for Lebanese reconstruction, with a further donation of $1 billion to be deposited in Lebanon's central bank to support the economy. Kuwait has pledged $300 million.
Siniora thanked Arab states for their donations, but said: "We want our [Arab] brothers to give renewed and concrete support - to cover all needs of the public and private sectors and to overcome an ordeal that has been going on for three decades."
The call came as Unifil 2, the expanded UN peacekeeping force in southern Lebanon, criticised Israeli incursions into Lebanese airspace.
Amir Peretz, the Israeli defence minister, has told a parliamentary committee that French peacekeepers in Lebanon have warned Israel that their jets may be targeted if they continue to violate Lebanese airspace.
"They said that Israeli planes fly over them and that there is no certainty that they won't open fire at them," Peretz told the parliamentary foreign affairs and defence committee on Monday, according to an official who attended the meeting.
Israel says its overflights do not contradict UN Security Council Resolution 1701, which included the ceasefire that brought an end to 34 days of fighting between Israel and Hezbollah on August 14.
The resolution calls for both sides to respect the border drawn by the UN after Israel ended its 18-year occupation of southern Lebanon in May 2000.
Apparently referring to information gathered from the overflights, Peretz said that Israel has collected evidence of Syrian involvement in the arms smuggling and that "if the transfer of weapons to Hezbollah becomes systematic, we will have to take care of it ourselves".
The Lebanese army denied the charge on Tuesday, saying it is in control of the border, and Peretz's comments on the transfer of weapons to Hezbollah were "an excuse to continue with the aggression on Lebanon through extensive air violations and violations of Resolution 1701".
Despite warnings from both sides about alleged violations that could rekindle the fighting, the truce has held, with no serious violence on either side.
Israeli warplanes have been overflying Lebanon routinely for decades, gathering intelligence, making their presence known and setting off sonic booms over Beirut.
The French foreign ministry last week condemned the overflights and announced that France was working with the UN to "organise the rules of managing the Lebanese airspace" in response to Israeli violations.
"We want our [Arab] brothers to give renewed and concrete support"
Lebanese Prime Minister
However, Alexander Ivanko, the Unifil spokesman in southern Lebanon, said he was unaware of any threats to shoot at Israeli planes. "I am not aware of any such comment made by any Unifil officer."
Meanwhile, Unifil's acting commander said in a statement that minor technical issues were delaying the complete withdrawal of Israeli troops from south Lebanon. There are still small troop contingents in border villages, particularly the village of Ghajar.
JP Nehra, a brigadier-general, said he expected the Israel full withdrawal would be made soon.