Israel's military said it had intercepted a "suspicious aerial target" on Friday off the northern port city of Haifa amid high tension along its frontier with Lebanon.
The seaports of Haifa and Ashdod are crucial gateways for Israel's trade.
An Israeli military spokesperson said the target had not caused any damage or injuries.
"I cannot confirm exactly how close it was to the port, but the fact that, according to protocol, no sirens were sounded means that it was far enough," the spokesperson said, declining to say whether the target or its source had been identified.
In December, the Israeli military said it had intercepted a drone that had crossed from Lebanon, triggering sirens in Haifa's suburbs.
The military said the target had been intercepted within Haifa's maritime zone, which extends 25 nautical miles from the shore, according to a maritime security source.
Israel and the Iranian-backed Lebanese group Hezbollah have engaged in their deadliest cross-border hostilities in over 17 years, prompted by an attack on Israel from Gaza by the Palestinian militant group Hamas that triggered a major Israeli offensive on the coastal strip.
Having evacuated tens of thousands of residents from areas near the Lebanese border, Israel has threatened to escalate fighting there unless Hezbollah stops cross-border attacks.
While officials have said Israel's ports are protected by air defence systems, there are growing industry concerns over the impact on Haifa of any major escalation with Hezbollah.
Reporting by Jerusalem bureau and Jonathan Saul