JERUSALEM, Dec. 7 - An Israeli airstrike killed a Palestinian militant in the southern Gaza Strip and wounded at least nine other Palestinians on Wednesday as Israel stepped up military actions in the wake of a suicide bombing.

The Israeli attack killed Mahmoud Arkhan, a leader of the Popular Resistance Committees, as he rode in a sedan in Rafah, on Gaza's border with Egypt, Palestinian security officials and hospital workers said.

The car was destroyed and three men riding with Mr. Arkhan were wounded, as were six people on the street, said staff members at Al Najar Hospital in Rafah.

The Israelis struck two days after a suicide bomber from the Islamic Jihad faction in the West Bank killed five Israelis in a blast at a shopping mall in Netanya on the coast.

Israel's defense minister, Shaul Mofaz, warned that Israel would hit back hard, and the strike on Wednesday was a return to killings directed at specific targets by the Israeli military in Gaza. Israel withdrew settlers and soldiers from Gaza in August and September. Since then, Palestinian militants and the Israeli military have periodically exchanged long-range fire across the Gaza frontier. Israeli airstrikes have been less frequent, though seven Palestinians were killed in aerial attack on Oct. 27, a day after a suicide bombing killed several Israelis in Hadera.

The military said Mr. Arkhan had a role in attacks on Israeli troops, including the killing of a soldier in June. The Popular Resistance Committees, made up of militants from various groups, fired rockets into Israel from Gaza in recent months.

In Israeli politics, Prime Minister Ariel Sharon's new, centrist party, Kadima, gained another high-profile member on Wednesday, when Tzachi Hanegbi, a cabinet member, announced he was quitting as acting chairman of the right-wing Likud Party to join Mr. Sharon.

Mr. Sharon left Likud two weeks ago to form Kadima in preparation for Israel's March 28 parliamentary elections. Several opinion polls, including one released Wednesday, show Mr. Sharon's new party far ahead of its rivals.

"The strategic steps necessary to fashion the state of Israel can be led only by Prime Minister Ariel Sharon," Mr. Hanegbi said.