Israel accuses Syria of routine weapon smuggling to Lebanon's Hezbollah.
Brigadier General Yossi Baidatz, the head of Israel's military intelligence research department, told a parliamentary committee on Tuesday that Hezbollah's arsenal included thousands of rockets of all ranges and types, some solid-fuelled.
Baidatz did not specifically name the long-range Scud missiles which Shimon Peres, the Israeli president, had accused Hezbollah of stockpiling, but appeared to allude to Peres' warnings.
"The shipments of long-range missiles which have been reported recently are only the tip of the iceberg," he told the Foreign Affairs and Defence Committee.
"Syria has a significant role in the growing strength of Hezbollah's rocket arsenal. Weapons are sent to Hezbollah from Syria on a regular basis under the direction of the Syrian and Iranian regimes," he said.
Hassan Nasrallah, the head of Hezbollah, refused on Saturday to confirm or deny the Scud allegations, saying his group has a "legal" right to own any weapons it wishes.
"We do not confirm or deny if we have received weapons or not, so we do not comment and we will not comment," Nasrallah said.
Hezbollah, which is backed by Iran and Syria, is the only group that did not disarm after Lebanon's 1975-1990 civil war, arguing its weapons are necessary to fight Israel, which it later faced off in a devastating conflict in 2006.
On Monday, President Barack Obama renewed US sanctions on Syria for a year, accusing Damascus of supporting "terrorist" groups and pursuing missile programmes and weapons of mass destruction.
Hillary Clinton, the US secretary of state, warned Bashar al-Assad, the Syrian president, last week about the risks of sparking a regional war if he supplied long-range Scud missiles to Hezbollah.