At least three Palestinians have been killed by tank fire near the border between Israel and the Gaza Strip, reports say.
Medical staff and witnesses said Israel fired shots across the border near the town of Beit Hanoun in Gaza.
One report said the two of those killed were a 91-year-old man and his 33-year-old grandson.
Militants in the Hamas-run Gaza Strip earlier fired a rocket into Israel but no casualties or damage were reported.
Adham Abu Salima, a spokesman for medical services in Gaza, told AFP news agency that the 91-year-old victim had been a caretaker at a farm.
His grandson died shortly afterwards from his wounds, he said.
The identity of the third victim was not yet clear.
Israeli army radio described the people killed as "terrorists" and said that at least one of them was armed.
The BBC's Jon Donnison in Ramallah says there has been an increase in rocket fire from Gaza in the past week, although it is nearly always ineffectual.
One Thai farm worker in Israel has been killed by rocket fire from Gaza in the past 18 months while scores of Palestinians in Gaza have been killed over the same period.