JERUSALEM (AFP) - A rocket fired from Lebanon struck northern Israel early Friday, causing troops to hit back with artillery fire over the border, the Israeli army said.

The rocket crashed into a field near Kfar Yuval, between Metula and Kiryat Shmona at Israel's northernmost tip, a spokesman told AFP.

"A rocket fired from Lebanon hit an open area near Metula. In response, IDF (army) forces opened fire at the source of rocket fire," an army statement said.

Israeli army spokesman Lieutenant Colonel Peter Lerner said artillery units had fired a barrage at "suspicious positions" sighted over the border.

Public radio said two Katyusha rockets slammed into an area north of Kiryat Shmona, one of which struck a road which was deserted at the time.

Military officials told the radio said they believed the rockets were fired by a small Palestinian group in an act of solidarity with militants from Gaza's Islamist Hamas movement who are engaged in a major confrontation with the Israeli army which began on Tuesday.

They said it was unlikely the rockets were fired by the Shiite Hezbollah movement, which controls southern Lebanon, as it did not want pick a fight with Israel at this stage.

A Lebanese security source confirmed the incident, but said the number of rockets fired was "up to three".

"The Israelis fired back, launching some 25 shells at the outskirts of Kfar Shuba," he told AFP on condition of anonymity, referring to a village in the south.

"No one was hurt, the shelling hit the fields, not houses. The situation at the border is now calm, and one man has been detained by the security forces for questioning," the security source added.

Lebanon's official National News Agency also reported "25 shells" launched by Israel in response to the rocket fire.