Damascus has admitted to shooting down "an unidentified aerial target" late Friday, saying it had violated Syrian airspace over coastal waters. The state-run Syrian news agency SANA quoted a Syrian military spokesman as saying the plane came "from the west at a very low altitude and at high speed over territorial waters."

In response, Turkish President Abdullah Gul said it could not be ignored that Syria had shot down the fighter jet and that it might have crossed into Syrian airspace.

"It is not possible to cover over a thing like this," Gul said. "Whatever is necessary will no doubt be done," Turkish news agency Andalou quoted him as saying.

"It is routine for jet fighters to sometimes fly in and out over [national] borders ... when you consider their speed over the sea. These are not ill-intentioned things but happen beyond control due to the jets' speed," Gul said during a visit to the central Anatolian city of Kayseri.

An investigation would look into the question of whether the F-4 Phantom jet was downed while still inside Turkish airspace, he said.

Turkish media reported that Turkish and Syrian coast guards were continuing a joint search to locate the wreckage of the plane and its two missing pilots in waters off Syria's Mediterranean coastline region of Latakia.

This latest crisis will likely inflame relations already strained over Turkish Prime Minister Recep Tayyip Erdogan's outspoken condemnation of Damascus and its handling of the Syrian uprising. Previously the two nations had been close.

Conflict continues

UN-Arab League envoy Kofi Annan has urged world powers to increase pressure on both sides in the Syrian conflict, which monitors say has cost more than 15,000 lives since March 2011. Foreign observers have increasingly termed the conflict a civil war.

According to the Syrian Observatory for Human Rights, at least 15 people were killed by troops across the country on Saturday.

Meanwhile, the Syrian state news agency said that Assad had created a new government, but left loyalist members of his Baath Party in charge, including Riyad Hijab as the new prime minister. Hijab is a former agriculture minister.

Assad retained his foreign, defense and interior ministers in the cabinet.

After the May 7 parliamentary elections - which the opposition boycotted - the president had promised to make government more inclusive.

sb, ipj/jlw (Reuters, AFP, dpa)