SQL & PL/SQL

I have a procedure

create or replace procedure abc
(p_username in all_users.username%type)isbegin execute immediate 'alter user ' || p_username || ' account unlock';end;


I need to call this procedure from sqlplus.

I tried below but get error.

execute unlock_account ('usermane');
BEGIN unlock_account ('username'); END;

*
ERROR at line 1:
ORA-00940: invalid ALTER command
ORA-06512: at "schema.abc", line 3
ORA-06512: at line 1

DN