GAZA CITY, Gaza Strip — Palestinian Arab fighters in the Gaza Strip fired a Katyusha rocket 10 1/2 miles into Israel yesterday, their deepest artillery strike yet, provoking some of the heaviest Israeli assaults in months. Nine Palestinian Arabs were killed in the day’s fighting.

The rocket landed harmlessly on the northern outskirts of the coastal city of Ashkelon. An Israeli tank and helicopter offensive that was already under way in Gaza quickly intensified, targeting suspected arms depots, and homes and hide-outs of militants, who fired back with grenade launchers and automatic rifles.

Palestinian Arab medical workers said three of those killed were civilians — the mother, sister, and brother of a man from the Islamic Jihad group, who also died when a tank shell ripped through their home in the city of Khan Yunis. Israel said it was responding to gunfire from the house.

More than 30 Palestinian Arabs, including five children, were reported wounded as the fighting spread from Khan Yunis to Gaza City and Rafah.

A Palestinian Authority spokesman, Nabil Abu Rdeneh, called the Israeli offensive “a bloody message” that could tarnish President Bush’s visit to the region next week.

Mr. Bush is coming to measure progress in peace talks that he launched between Israel and the Palestinian Authority in November at a conference in Annapolis, Md.

“They are killing the spirit of Annapolis,” Abu Rdeneh said.

An Israeli government spokesman, Mark Regev, said the army operations were defensive, aimed at stopping rocket fire from Gaza. The coastal strip is ruled by the militant Hamas movement, which advocates Israel’s destruction and is not involved in the peace talks.