The Israeli Prime Minister, Mr Ariel Sharon, said today his forces were preparing "a massive operation".
He made the pledge today after a helicopter strike killed two Hamas militants.
"We are preparing a massive military operation against Hamas in the Gaza Strip, a taste of which you got this morning," Mr Sharon told members of his right-wing Likud party.
Earlier today, helicopter-fired missiles killed six Palestinians, including two officials of the militant group Hamas, riding in two cars in the southern Gaza Strip.
Hamas has stepped up anti-Israeli attacks in recent weeks, claiming responsibility for a devastating suicide bombing on a Jerusalem bus that killed 19 Israelis last Tuesday.
The group is now under pressure from both Israel and the Palestinian Authority, which placed its 66-year-old blind spiritual leader, Sheikh Ahmed Yassin, under house arrest today.
Hamas officials and the group's armed wing, the Ezzedin Al-Qassam Brigades, denounced both the Israeli raid and the house arrest, which came a day after several Hamas militants were rounded up by Palestinian police.
The Ezzedin Al-Qassam Brigades said in a statement, "We will continue the march of the Jihad and resistance, and will step up suicide operations. This is our reply to occupation."
AFP