SQL & PL/SQL :: Getting Minimum Composite Key From Group By

I have the following case:

create table try_o
(pk1 NUMBER, pk2 NUMBER, fld1 VARCHAR2(10), fld2 NUMBER,
PRIMARY KEY (pk1, pk2));
insert ALL
into try_o values (1,1,'f1',5)
into try_o values (1,2,'f1',5)

[Code]....

I need to get the row that contains the least pk2 among the group of records with the same fld1 and fld2. but if I used

select min(pk1), min(pk2), fld1, fld2
from TRY_o
group by fld1, fld2;

I get a record that doesn't exists as the min(pk1) and min(pk2) are from different records. I need to get the min(pk1) and its corresponding pk2.