Turkey’s special military force carried out an unusual weekend operation against Islamic State fighters in Syria as part of a deepening campaign against the extremist group, U.S. officials said on Tuesday.

A small group of elite Turkish soldiers entered Syria on Saturday to help more effectively target Islamic State fighters who have been launching rocket attacks into Turkey for weeks, American officials said.

Turkish officials declined to comment on the military operation. Turkish President Recep Tayyip Erdogan on Tuesday said all options were on the table for bringing the Islamic State rocket strikes to an end.

“What’s going on in Syria is a historic showdown,” said Mr. Erdogan, who has unsuccessfully pushed the U.S. and its allies to use their military might to create a protected buffer zone in northern Syria for rebel fighters and Syrian civilians looking for safety from the conflict.

The operation was part of an expanding effort by the Turkish military to push Islamic State away from a vital 60-mile stretch of the Turkey-Syria border that serves as the group’s main lifeline, according to U.S. officials.

While Turkey released no details, U.S. officials informed of the operation said it appeared to be an intelligence gathering effort to help Turkish forces better locate and target Islamic State positions.

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