Israeli submarines have reportedly been spotted off the coast of southern Lebanon.

French UNIFIL forces in southern Lebanon said they saw the Israeli subs on several days, traveling from Nakura past Tyre and as far north as Sidon, the Israeli newspaper Maariv reported Monday, citing Lebanese news site Addiyar Online.

The report said the UN had been apprised of the Israeli movement, but Hezbollah had not received word of it.

In recent weeks, Lebanon several times accused Israel of violating Lebanese airspace by sending “spy” drones on overflights and conducting mock sorties.

Israel has not responded to the allegations.

In late January, US officials told The New York Times that Israel had notified the United States about an airstrike it carried out near the Lebanese-Syrian border. The officials said that they believed the target of the strike was a convoy carrying sophisticated anti-aircraft weaponry intended to reach Hezbollah forces in Lebanon.

An unnamed Western official told The Wall Street Journal that the convoy was carrying sophisticated Russian-made SA-17 anti-aircraft weapons, which could constitute a strategic game-changer were Hezbollah to possess them.

A former Syrian general said later that week that the facility reportedly struck by Israel produced nonconventional weapons, in addition to conventional arms. Maj. Gen. Adnan Sillu was previously in charge of the country’s chemical weapons training program.

Israel never officially commented on the alleged air raid.

On Saturday, Hezbollah leader Hassan Nasrallah warned of a very harsh response should Israel choose to attack Lebanon.

“The Islamic resistance won’t keep mum on any Israeli attack on Lebanon,” Nasrallah said, adding that Hezbollah would not need to transfer any weapons from Syria to retaliate. “The resistance in Lebanon possesses all the necessary equipment.”