Details are emerging of an apparent raid by Israeli special forces on a "Hezbollah missile production facility" in Syria.
Israel's government has said nothing about the operation which, according to US media reports, took place at the beginning of the week.
Syrian state media say 18 people were killed on Monday in the raid near the Syrian city of Masyaf - around 25 miles (40km) north of the Lebanese border - and several dozen were injured.
According to the New York Times, Israeli special forces descended from helicopters, placed explosives inside the Iranian-built facility and removed sensitive information.
American and other officials quoted in the paper paint a picture of a daring operation, designed to destroy the underground military facility.
Air strikes were apparently used to neutralise Syria’s defences and prevent reinforcements from reaching the site.
Separately, a report by the Axios news site - citing three sources said to be familiar with the operation - says the elite Shaldag unit of the Israeli Air Force carried out the raid.
Axios also reports that Israel informed the US before the operation was slated to take place, and was not met with any resistance from the White House.
The BBC has not yet been able to independently verify these reports.
Israel's government has not commented, but the raid seems to have been designed to prevent Iran from supplying precision missiles to Hezbollah, its Lebanese ally and proxy.
Israel attacked the facility six years ago and has mounted dozens of air strikes against Syria since the war in Gaza began almost a year ago.
But, putting Israeli troops on the ground inside Syria is highly unusual.
This would be one of the most sophisticated operations of its kind in years.
Last Sunday, at least 18 people were killed in Israeli air strikes on a number of military sites in the vicinity of Masyaf, according to the Syrian health minister.
Israeli strikes have reportedly been stepped up since the start of the war in Gaza in October last year, in response to cross-border attacks on northern Israel by Hezbollah and other groups in Lebanon and Syria.
According to the Syrian Observatory for Human Rights (SOHR) - a UK-based monitoring group with a network of sources on the ground - Israeli air and artillery strikes have targeted Syrian territory on more than 60 occasions since the start of the year.
This has resulted in damage to or destruction of about 140 targets, including weapons depots, vehicles and Iran-backed militia headquarters, the SOHR said.
The strikes have killed at least 208 fighters - including 46 members of Syrian government forces, 43 members of Hezbollah and 24 Iranian Revolutionary Guards - as well as 22 civilians, the monitoring group added.
Source: BBC
