The Israeli army has conducted airstrikes on the Palestinian enclave controlled by Islamist movement Hamas in response to frequent rocket and mortar attacks on Israeli territory.
All three militants, members of al-Quds Brigades, an armed wing of the Palestinian Islamic Jihad, were travelling on a main Gaza Strip highway when a missile hit their car, TV channel Al-Aqsa said.
Earlier in the day, a Qassam rocket launched by Palestinian militants wounded a female resident of Sderot, an Israeli town by the border with Gaza, which has been a major target of Palestinian rocket attacks over the past seven years.
According to the Israeli military, since 2001 Palestinian militants have fired over 4,500 rockets and mortar shells at the town with a population of 22,000, including 20 mortar shells and about 30 rockets in the past week.
Tel Aviv has urged Palestinian authorities to put a stop to attacks by militants against Israel before any peace deal can be brokered.