EU regulators raid Romania's Romgaz, Transgaz, OMV Petrom

* Firms suspected of blocking gas exports to other EU countries

* Gazprom charged with similar offence a year ago (Adds Petrom to list of companies raided)

By Foo Yun Chee and Luiza Ilie

BRUSSELS/BUCHAREST, June 7 (Reuters) - EU antitrust regulators have raided Romanian state-owned gas producer Romgaz , gas pipeline operator Transgaz and top oil and gas firm OMV Petrom over suspected blocking of gas exports to other EU countries.

The European Commission said the raids took place on Monday but did not name the companies, in line with its usual policy.

Romgaz, Transgaz and OMV Petrom, controlled by Austria's OMV , said on Tuesday they were raided.

The EU competition enforcer charged Gazprom last year with a similar offence, a case which the Russian gas company is trying to settle with concessions to avoid a possible billion-euro fine.

Allowing cross-border gas sales is a cornerstone of the Commission's strategy to create a single energy market in the 28-country bloc.

"The Commission is investigating potential anticompetitive practices in the transmission and supply of natural gas in Romania, in particular relating to suspected anticompetitive behaviour aimed at hindering natural gas exports from Romania to other member states," the EU executive said in a statement on Tuesday.

Romgaz, one of two major gas producers in Romania, said it was a target of the raids.

"We confirm the inspection. It is ongoing and as a result we cannot comment over the motives," the company said.

State-owned Transgaz also confirmed the EU raid.

"OMV Petrom is cooperating with the European Commission within an inspection related to potential practices on the gas market in Romania, which could envisage restrictions of gas exports," the third company said, declining further comment.

Romania is one of the EU's least energy-dependent states. It produces the bulk of its gas locally and imports up to 8 percent of its needs from Russia.

However, its interconnections are not fully developed, meaning Romania can import significantly more than it can export. Its investment in making interconnections work both ways has been lagging.

(Reporting by Foo Yun Chee; Editing by Adrian Croft and Matthew Lewis)