No arrests have been made in the assassination of the President of Palau, an official of the Pacific island chain said today. He said a mistaken report of an arrest had apparently stemmed from confusion over an unrelated investigation.

Haruo I. Remeliik, 51 years old, the first and only President of the trusteeship, was shot and killed in the driveway of his home early Sunday.

''No suspect has been taken into custody at this point,'' Bonifacio Basilius, a presidential assistant, said today.

An arrest had been reported Sunday by Janet McCoy, High Commissioner of the Trust Territory of the Pacific Islands.

Palau, which has 14,000 people on eight inhabited islands, is administered by the United States as part of the Trust Territory under a United Nations mandate.