Israeli troops and tanks entered the northern Gaza Strip Sunday, hours after Israel ended an operation against Palestinian militants in southern Gaza.

The Beit Hanoun operation began soon after Israeli forces withdrew from Khan Younis after a three-day assault. Israel says both raids were aimed at stopping militants from firing rockets and mortar shells at Israeli settlements and towns.

The Israeli military actions come one week before Palestinian elections to replace the late Palestinian Authority President Yasser Arafat.

A new opinion survey by the Palestinian Center for Policy and Survey Research shows Palestine Liberation Organization chairman Mahmoud Abbas with a 65-to-22 percent lead over his nearest rival, Mustafa Barghouti.

Mr. Abbas has vowed to protect Palestinian militants from Israeli raids. He also has criticized attacks on Israelis, saying they are not productive.

Some information for this report provided by AFP and Reuters.