Israeli aircraft struck Hamas targets in Gaza during Sunday night, the Israeli military has said.
More than 230 rockets have been fired on Israel in the past 12 days
The strikes came after Israeli PM Ehud Olmert vowed to continue a crackdown against Hamas, following the death of an Israeli man in a rocket attack.
"No-one involved in terror has immunity," Mr Olmert told his Cabinet.
About 40 people have been killed in Gaza in 12 days of Israeli air strikes designed to stop the rocketing. Hamas said its attacks would not stop.
"We will not surrender, we will not raise the white flag," said spokesman Ayman Taha.
Attempts by Palestinian leader Mahmoud Abbas, who belongs to the rival Fatah faction, to revive a ceasefire with Israel and halt Hamas attacks have come to nothing.
"The truce must be reciprocal and implemented simultaneously in the Gaza Strip and the West Bank," said Mr Taha, after a meeting between factions in Gaza City on Sunday evening.
"The Israelis are continuing their operations and Ehud Olmert is refusing any truce. It's not the resistance that is to blame, it's the occupation."
Mr Olmert hinted that any Israeli action would be open-ended.
Olmert (far right) spoke after the weekly cabinet meeting
"We are not acting according to any timetable that is dictated externally. We will decide where, how and to what extent we act," he said.
The Israeli man died on Sunday morning after shrapnel hit him in the neck in the town of Sderot. Hamas militants said they had carried out the rocket attack.
One other Israeli civilian has been killed and 16 wounded by rockets fired on Israeli towns, particularly Sderot, in recent days.
According to the Israeli army, more than 230 rockets have been fired from Gaza since mid-May.
Mr Olmert's spokeswoman said that Israel would not only target those directly involved in the rocket attacks.
"If somebody in the hierarchy is involved in terrorism, they should not feel safe," said Miri Eisin.
On Saturday Israel arrested a Hamas member of the Palestinian cabinet, Wasfi Kabaha.
The arrest follows the detention on Thursday of Education Minister Nasser al-Shaer and about 30 other officials in the West Bank.
Hamas has warned that any Israeli attack against the group's military or political leaders would make the release of Israeli Corporal Gilad Shalit more uncertain.
Cpl Shalit has not been heard from or seen since his capture near Gaza in June 2006.