SQL & PL/SQL

Is it possible to create a securefile lob in PL/SQL to use the new dbms_lob procedures

Following block gives: "ORA-43856: Unsupported LOB type for SECUREFILE LOB operation"

DECLARE
l_clob clob;
BEGIN
l_clob := '1234';
dbms_lob.fragment_replace(lob_loc => l_clob
,old_amount => 2
,new_amount => 2
,offset => 2
,buffer => 'BC');
END;