Israel has stepped up military action against Gaza's Hamas rulers

Witnesses said Israeli troops backed by tanks and aircraft launched an incursion near Jabaliya sparking clashes with gunmen.

The teacher, 38, was killed when a surface-to-surface missile hit a school in Beit Hanoun in a separate raid.

There are no reports of Israeli casualties in the engagements.

Israel has stepped up military action against Hamas since it claimed responsibility for Monday's suicide bombing in Dimona - its first in Israel since 2004.

Hamas said an armed member of Islamic Jihad was killed along with its five members in fighting with the Israeli troops.

"What was the fault of a teacher, an emissary on a sacred mission?" the ministry said in a statement.

An Israeli military spokeswoman said troops had not targeted the school but had fired on a Palestinian rocket crew.

The army is checking whether the building was hit by a stray missile, she said.

Hamas says it has fired 40 rockets and 60 mortars at southern Israel since the new upsurge in fighting began with a deadly Israeli airstrike on Tuesday afternoon which killed seven Hamas security force members.

Correspondents say the violence threatens to overwhelm renewed peacemaking efforts spearheaded by the leader of Hamas's factional rival Fatah, Palestinian Authority President Mahmoud Abbas.

Hamas, does not recognise Israel and opposes the peace process. It ousted Mr Abbas's forces from Gaza in June, but he remains in control of Palestinian-administered parts of the Israeli-occupied West Bank.