International Petroleum Investment Company (IPIC) raised its stake to 24.9 percent from 20.4 percent, OMV said in a statement on Monday. This means is just shy of a blocking minority in the Vienna-based group.
Austrian state holding company OeIAG, OMV's biggest shareholder with 31.5 percent, said it welcomed the move.
"This underlines the attractiveness of OMV as a company with growth potential in its core markets," it said in a statement.
OMV is the biggest energy company operating in emerging Europe. It bought Turkish gas station operator Petrol Ofisi last year in a 1 billion-euro ($1.3-billion) deal and snapped up the Tunisian assets of Pioneer Natural Resources in January.
IPIC, which has been involved in OMV for 17 years, invests across the energy sector. It has stakes in 14 companies globally, including Spain's Cepsa, Ferrostaal, Canada's Nova Chemicals, Japan's Cosmo Oil and plastics maker Borealis, part-owned by OMV.
OMV said last month at its capital markets day in Istanbul that it would divest up to 1 billion euros of refining and marketing assets by 2014 to focus on its more profitable exploration and production business.
Some analysts have said OMV's target is too ambitious given the saturated market for such assets.
The news came as OMV came closer to receiving the first shipment of Libyan condensate since March, when civil war escalated in the country that used to supply a tenth of OMV's output.
OMV's shares extended losses to trade 2.82 percent down by 1409 GMT, more than the sector index which was down 1.6 percent.
