Israeli forces moved into the southern Gaza city of Khan Younis (search) early Wednesday, wounding at least 12 people in a missile strike, Palestinian officials said.

Israeli military officials confirmed that an operation "against the terrorist infrastructure" was in progress, and a helicopter fired a missile at an open area to deter gunmen.

Palestinian hospital officials said 12 people were wounded by the missile, three critically.

Israel often sends troops into Gaza (search) towns, cities and refugee camps, targeting militants and destroying structures they say gunmen use for cover.

There were no other immediate details of the action, which comes as Israel prepares to withdraw from some West Bank areas. Israeli Prime Minister Ariel Sharon (search) is promoting a plan he calls "unilateral disengagement," pulling all Israeli soldiers and settlers out of the Gaza Strip by late next year, as well as removing four small settlements.

In the months since he announced the plan, Palestinian groups have been jockeying for position to take power when the Israelis leave. Israel refuses to negotiate with the Palestinian leadership, charging that it is tainted by terrorism, leaving a potential power vacuum.