BEIRUT, FEB. 1 -- An Iranian-backed Shiite Moslem guerrilla group today threatened to kill an Israeli soldier taken captive in southern Lebanon two years ago unless Israel halts "brutal practices" against Palestinians in the occupied territories.

"An Israeli soldier taken prisoner by us is now in extreme danger and may meet his dark fate if the criminal Zionists do not put a halt to their brutal practices against our Moslem people in occupied Palestine," the Islamic Resistance Front warned in a statement delivered to a foreign news agency.

Although no photos accompanied the statement as proof of authenticity, its style resembled previous ones. The group said it sought to introduce "a new element to the confrontation with the enemy and to lend support to the blessed uprising in the occupied homeland."

Two Israeli soldiers, Yossi Fink and Rahamin Alsheikh, were seized by Shiite Lebanese guerrillas on Feb. 16, 1986, during a firefight on the edge of the security zone that Israel has declared in southern Lebanon.

Their capture by pro-Iranian Hezbollah fighters prompted an Israeli military sweep into several villages north of the zone.

Three days after they were captured, an anonymous caller claiming to represent the Islamic Resistance Front -- a coalition of guerrilla groups that includes Hezbollah -- said one of the two had been killed because Israel failed to halt its search operation in Lebanon. The death has never been confirmed.

Describing the Israeli response to the protests in the occupied territories as "bloody and hysterical," the Resistance Front praised the Palestinians' "Islamic awakening," which it said has succeeded in throwing Israeli authorities into a "state of disarray."

"We and the world have watched how Israeli helicopters have been bombing civilians in revolt with suffocating gases and tear gas," it said.

Meanwhile, a mediator seeking freedom for two French youngsters held by the Abu Nidal group said the group was not ready to release them.

A spokesman for the Abu Nidal group said the two sisters, ages 5 and 6, did not want to leave their mother. They are part of a group of eight French and Belgian citizens seized from a yacht off the Gaza Strip on Nov. 8 and accused by the captors of being Israeli spies.