ORA-08104: this index object is being online built or rebuilt.

While creating an index , related session has been killed.When trying drop index
or rebuild it following error occured.

ORA-08104: this index object <object_id> is being online built or rebuilt.

SMON should do clean up process.But there must be no transaction against the table in order to SMON be successfull.
To do this application can be stopped and wait until cleanup is done.

For 10.1 SMON need to be waited to finish process,After 10.2 DBMS_REPAIR.ONLINE_INDEX_CLEAN() can be used.

Following script does this cleanup process.

declare
  ret boolean;
begin
  ret=sys.dbms_repair.online_index_clean(&OBJECT_ID);
end;