BEIT HANOUN, Gaza Strip — Hamas’ military wing called Wednesday on Muslims around the world to attack American targets and abandoned their truce with Israel following reports that an Israeli tank strike killed 18 people in the Gaza Strip.

The threat signaled a possible change in tactics by Hamas militants, who have historically directed their homicide bombings and rocket attacks only against Israeli targets.

“America is offering political, financial and logistic cover for the Zionist occupation crimes, and it is responsible for the Beit Hanoun massacre. Therefore, the people and the nation all over the globe are required to teach the American enemy tough lessons,” Hamas said in a statement sent to The Associated Press.

“The truce (with Israel) ended at the end of 2005,” Mashaal told a news conference in the Syrian capital hours after the Israeli tank shelling of Beit Hanoun in Gaza. “The armed struggle is free to resume, and the resistance is dictated by local circumstances.”

The truce that Hamas and a second militant group declared with Israel early last year had expired on Dec. 31, but it had continued to be honored, with some infractions.

Mashaal’s statement Wednesday made it clear that from now on, the gloves were off and Hamas guerrillas would strike at will.