* Q2 pretax profit trebles to 139 mln euros
* Q2 gross premiums dip 3.1 pct to 2.25 bln
* Q2 combined ratio improves to 97.9 pct (Recasts with Q2 figures, adds quotes and background)
VIENNA, Aug 26 Vienna Insurance Group trebled second-quarter pretax profit to 139 million euros ($183.6 million) as its struggling Romanian business continued to generate profit, emerging Europe's biggest insurer said on Tuesday.
Gross premiums fell 3.1 percent to 2.25 billion euros in the quarter, while its combined ratio - a measure of profitability in the property and accident segments - improved to 97.9 percent from 102.9 in the year-earlier quarter.
Analysts polled by Reuters had on average expected second-quarter profit of 143 million euros, gross premiums of 2.39 billion and a combined ratio of 96.8 percent.
The group said the combined ratio improved despite its conservative reserving policy for the Italian business of its Donau Versicherung business and severe weather claims, particularly in Austria, Serbia and Bosnia-Herzegovina.
Vienna Insurance said in May first-quarter profit fell 4.7 percent, slightly less than expected, as the group made money in all of its central and eastern European markets for the first time since the financial crisis began.
It has forecast Romanian operations will return to profit this year after a 75 million euro writedown in 2013 to reflect tough competition. It made 1 million before tax there in the first half.
One-off effects in Italy and Romania had contributed to a 2013 group pretax profit drop of 37 percent to 355.1 million euros.
Vienna's Italian car insurance business posted heavy losses last year after getting a flood of claims from customers across the country. It has scaled back its Italian business, cut ties with many brokers, changed local management and focused on customers in northern Italy. (1 US dollar = 0.7569 euro) (Reporting by Michael Shields; Editing by Mark Potter and Louise Heavens)