Reuters TV footage showed one impact site near a bus stop on a main road outside the city.
In a statement, the Israeli military said sirens sounded around Acre but that turned out to be a false alarm.
It said its air force struck two Hezbollah facilities in south Lebanon.
Fears are rising that the Middle East could be tipped into full-blown war following vows by Hezbollah to avenge Hezbollah commander Fuad Shukr’s killing, and by Iran to respond to the assassination in Tehran last week of the head of Palestinian militant group Hamas.
A Hezbollah source told Reuters that “the response to the assassination of commander Fuad Shukr has not yet come”.
Earlier on Tuesday, four people were killed in a strike on a home in the Lebanese town of Mayfadoun, nearly 30km north of the border, medics and a security source said.
Two additional security sources said those killed were Hezbollah fighters but the group had not yet posted its usual death notices.
Hezbollah and the Israeli military have been trading fire for the last 10 months in parallel with the Gaza war, with the tit-for-tat strikes mostly limited to the border area.
Last week, Israel killed Shukr, Hezbollah’s senior-most military commander, in a strike on the group’s stronghold in the southern suburbs of Lebanon’s capital Beirut.
Hezbollah’s leader, Sayyed Hassan Nasrallah, vowed revenge, but said the response would be “studied”.
