The Lebanese television channel LBC reported on Sunday night that an Israeli warship had entered Lebanon's territorial waters.
The ship reportedly crossed over near a beach near Kibbutz Rosh Hanikra.
The ship was detected by UNIFIL forces who informed Lebanese authorities of the suspected breach, according to LBC.
Israel has not commented on the incident.
Lebanon and Israel, which have no official diplomatic ties, also have a longstanding dispute over the maritime border between the two countries.
Last year, Lebanon signed its first contract to drill for oil and gas off its coast with a consortium comprising energy giants Total, ENI and Novatek, including in a block disputed by Israel.
Israel says one of two blocks in the eastern Mediterranean where Lebanon wants to drill for oil belongs to it, and had denounced any exploration by Beirut as "provocative".
In May, Energy Minister Yuval Steinitz said Israel had agreed to enter US-mediated talks with Lebanon on the maritime borders.