Palestinian officials say four people, including a mother and two of her sons, were killed late Wednesday, during an Israeli military operation in the Gaza Strip.
Israeli tanks have fired on the coastal village, Sheikh Ajli, in the Gaza Strip.
Medical personnel in the area report casualties, including the deaths of a mother and two of her sons.
The spokesman for the Israeli Defense Forces says the incident is being investigated.
For the past two days, Israel has been deploying army, naval and air forces to foil what it says is a Palestinian attempt to smuggle arms into Gaza by sea.
Israeli tanks moved into Palestinian territory, near the Jewish settlement, Netzarim, cutting off a main road, as Israeli gunboats patrolled the coastline.
Earlier, one Palestinian was shot dead by Israeli forces near the Gush Katif bloc of Jewish settlements, also in the Gaza Strip.
Tuesday, Israel called off high-level talks with Palestinian officials on a security plan, citing continuing violence in the territory.
Israeli Defense Minister Binyamin Ben-Eliezer says he expects the Palestinians to be vigorous in halting what he calls "terrorism and violence, as well as smuggling [of arms] by sea and on land."
A spokesman for Palestinian leader Yasser Arafat, accuses Israel of abandoning an agreement to withdraw its troops from Palestinian self-rule areas.