The spiritual leader of Hamas has vowed to continue to attack Israel.
The call comes a day after the group carried out a suicide bombing south of Tel Aviv that killed 15 Israelis.
Sheik Ahmed Yassin said Israel's military operation in the West Bank had not crippled the organisation.
The blind and paraplegic Yassin said: "The Palestinian people will continue the armed struggle and resistance as long as occupation exists on our land. We fear God only and we don't fear the aggression."
Hamas has taken responsibility for Tuesday's bombing in Rishon Letzion, 10 miles south of Tel Aviv. The bomber walked into the pool hall with a suitcase and a belt packed with 2.8lb of explosives and metal objects.
Hamas did not identify the bomber. Yassin said the Palestinians had no other means of defence in facing the Israeli military offensives than attacking Israelis.
Yassin said: "When they harm and hurt Palestinian civilians their civilians will be harmed. Sharon began this war and this is a normal reaction to the Israeli massacres against Palestinians."
Palestinian officials said they expected Israel to target Gaza, where Hamas is based. Mr Yasser Arafat placed Yassin under house arrest as part of a crackdown on militants in December but later released him.
Mr Arafat has condemned the bombing and ordered his crippled security forces to go after those responsible for terrorist attacks against Israeli civilians.