** nib Group NHF.AX rises as much as 4.4% to A$6.82
** Stock hits highest since February 18, a day after co announced higher health insurance premiums post market
** Co posts HY underlying operating profit of A$129.1 mln ($91.6 mln), up from year-ago A$105.8 mln
** YTD, NHF down 0.9%
($1 = A$1.4094)
(Reporting by Nichiket Sunil in Bengaluru)
((Nichiket.Sunil@thomsonreuters.com))