JERUSALEM — Israel announced yesterday that it would increase airstrikes on Hamas in Gaza, targeting leaders of the group until its rockets attacks into Israeli territory ceased.

An emergency Security Cabinet held off ordering a wider ground operation in Palestinian Arab territory. Prime Minister Olmert said military operations would focus on the Hamas and Islamic Jihad militants he said were responsible for the past week’s attacks.

“If these strong steps don’t bring about calm, the Cabinet will meet to weigh more drastic steps,” he added. After sundown, an Israeli plane fired a missile at the house of a Hamas member of parliament, Khalil al-Hayya. Hospital officials said at least six people were killed and 13 injured, though Mr. Hayya was not at home.

Israeli airstrikes have killed at least 21 Palestinian Arabs since Wednesday, and earlier yesterday missiles hit a car carrying suspected militants and weapons, killing three people.

More than 150 makeshift rockets have been launched from Gaza since Tuesday evening, though less than half have landed inside Israel. Fourteen people have been injured, two seriously, and thousands of people have fled Sderot, a primary target and the hometown of the Israeli defense minister, Amir Peretz. Yesterday the town was given formal “frontline” status.