CAIRO — Turkey’s president said Saturday that his country would do “whatever is necessary” in response to the downing of a Turkish military jet by Syria, adding a new complication to the tense relationship between the former allies split by Turkey’s support for Syrian rebels trying to overthrow the government.

“It is not possible to cover over a thing like this,” said President Abdullah Gul of Turkey, according to the Anatolia news agency. “Whatever is necessary will no doubt be done.”

Syria said Friday that its military forces had shot down a Turkish jet that had entered its airspace just off the Syrian coast. But Mr. Gul said Saturday that while the exact route of the plane had not yet been confirmed, it was routine for military jets flying at high speeds to briefly cross into another country’s airspace, and that the jet’s presence over Syrian territory was not intended as a hostile act.

The plane went down over the Mediterranean off the coast of the Syrian province of Latakia and south of the Turkish province of Hatay. On Saturday, Turkish officials confirmed that parts of the jet had been recovered.