In his speech to the General Assembly, Netanyahu showed maps that were said to show that missiles are stored next to a gas station and a residential building in the Jnah district in southern Beirut.
He also showed photographs that were allegedly taken by the Israeli intelligence service.
A photo showed the entrance to what he said was a missile factory.
"This is where the next explosion will take place, right here," Netanyahu said.
Call for the Lebanese people
The Israeli Prime Minister called on the Lebanese people to act and protest.
"... because if this explodes, we will face a new tragedy."
In early August, a powerful explosion shook the port of Beirut.
Nearly 200 people were killed and 300,000 people became homeless when 2,750 tonnes of highly explosive ammonium nitrate stored centrally in the port detonated.
The ammonium nitrate that can be used both as a fertilizer and in bombs had been stored in the port of Beirut for years.
Hezbollah: Lies
Hezbollah leader Hassan Nasrallah gave a televised speech on Tuesday night in which he dismissed Netanyahu's allegations as lies.
"We do not store missiles near the port or near petrol stations.
We know how to store missiles, "said Nasrallah.
"Recently, the Prime Minister of the enemy spoke in a speech directly to the United Nations and said things with the aim of pitting the Lebanese against Hezbollah, as usual," Nasrallah said.
The Iranian-backed Shia Muslim Hezbollah movement has great political power in Lebanon and, along with its allies, has a majority in the Lebanese parliament.
The movement's armed branch is taking part in the war in Lebanon's neighbor Syria.
Hezbollah is stamped as terror by Germany, Britain and the United States, among others.
Israeli Prime Minister Benjamin Netanyahu addressed the UN General Assembly.
Photo: Rick Bajornas / UNITED NATIONS / AFP