Israel has massed troops and tanks at the Gaza frontier and has given a free hand to security forces to stop Palestinian cross-border rocket attacks.
Palestinian President Mahmoud Abbas accused Israel of undermining his efforts to calm violence but said he would do "all we can" to prevent further rocketing.
The worst surge in bloodshed since a truce was agreed in February has threatened to hamper Israel's withdrawal from Jewish settlements in occupied Gaza, starting next month, and amplified doubts over prospects for peacemaking.
Israeli Prime Minister Ariel Sharon said he had instructed the army "to act without limitation to stop the strikes on Israeli communities" after rocket and mortar bombardments.
But he later hinted Israel would not be quick to launch a major incursion into Gaza, telling his cabinet he would "weigh our response" to further truce violations.
Israeli political sources said a new Israeli offensive into the occupied territory was unlikely before US Secretary of State Condoleezza Rice visits later this week to try to salvage the crumbling ceasefire.
Six more Israelis were injured in rocket and mortar barrages yesterday. In the southern Gaza Strip, Israel killed Saeed Seyam, a commander of Hamas, with a shot from a settlement. The army called it part of a revived assassination policy.
Israel said its soldiers also killed a gunman nearing a settlement in central Gaza.
In northern Gaza, an Israeli aircraft fired missiles at a car carrying three Hamas militants leaving a site in Beit Lahiya used to fire rockets at Jewish settlements, witnesses said. The militants jumped out but one was wounded by shrapnel.
Mr Abbas reiterated a pledge to help curb the violence, telling reporters in Gaza: "We will do all we can to prevent these rockets . . . we are determined to prevent these rockets, regardless of the price."
But he condemned Israel for its assaults and for threatening a new military offensive, and said he had sought US intervention to prevent it.
He also accused Mr Sharon of looking for excuses to delay Israel's withdrawal from Gaza, planned for mid-August.
Mr Sharon, who ordered the army to step up action against militants after a suicide bombing and rocket attack killed six Israelis last week, has vowed not to quit Gaza under fire.
Egyptian officials met Hamas leaders in Gaza to try to help shore up the truce. A Hamas spokesman said afterwards that the group had a right to "resistance and self-defence" but remained committed to what he called "a conditional calm".
He also said the group would seek an end to
there days of fighting with Palestinian police that have raised fears of civil war. Two children have been killed and more than 20 people wounded.