There has been violence between the Israeli army and Palestinian protesters in the Gaza Strip since late March in which at least 155 Palestinians have been killed.
Hamas has pledged revenge after Israeli air and artillery strikes on the coastal enclave killed a number of its members in recent weeks.
Israel and Hamas have fought three wars since 2008.
A week ago a Palestinian gunman shot and killed an Israeli soldier at the border, sparking a fierce wave of Israeli bombing that ratcheted up fears of another war.
A degree of calm was restored until Wednesday when Israel said its troops came under fire again, with one soldier wounded.
It hit back with artillery fire which killed three Palestinians at a Hamas military base, near the border, east of Gaza City.
The al-Qassam Brigades, the military wing of Hamas, warned in response on Wednesday that “the enemy shall pay a high price in blood for the crime which it commits daily against the rights of our people and our fighters”.