WARSAW (REUTERS) - A lawyer arrested in Poland on suspicion of spying for a foreign state worked on a Polish gas project which officials view as strategically vital because it will cut dependence on imported Russian gas.

Polish law only allows the man, arrested on Wednesday, to be identified by his first name and the first two letters of his surname: Stanislaw Sz.

According to a profile on the website of law firm Stopczyk & Mikulski, that listed him as an employee, Stanislaw Sz. was a member of the legal team working on a project to build a terminal for importing liquefied natural gas at Poland's Baltic Sea port of Swinoujscie.

His employment at the law firm was confirmed by a source who knows the arrested lawyer.

There has so far been no comment on the allegations of spying from the Russian authorities. It was not immediately possible to reach lawyers representing the suspects.

The terminal is scheduled to come on stream next year, initially importing gas from Qatar, and Polish officials say it will give Poland an alternative to supplies from Russian gas giant Gazprom.

The Polish government believes its current dependence on Russian gas threatens national security because Warsaw has fraught relations with Moscow. These have been aggravated by the standoff between Russia and the West over Ukraine.

No one answered calls to the law firm's office on Friday evening or Saturday morning, and the firm did not respond to an e-mailed request for comment.

The lawyer was arrested on Wednesday by Poland's Internal Security Agency, along with a second spying suspect - a lieutenant-colonel in the Polish military.

Prosecutors announced the arrests, but did not reveal the country the men are alleged to have been working for.

A Polish lawmaker briefed on the case by intelligence officials said they are suspected of being Russian agents.

A Reuters reporter saw the lawyer who is under arrest being escorted in handcuffs along a corridor on Friday in a Warsaw court building where a judge ordered him held in custody for three months pending trial.

On the Internet site of the law firm, Stopczyk & Mikulski, Stanislaw Sz. is not listed as a current employee. However, his employee profile can be viewed on a cached page of the website.

It was not immediately clear when he worked on the gas terminal project, or in what capacity.

The arrested lawyer has been charged with cooperating with foreign intelligence to the detriment of Poland, a spokesman for Warsaw prosecutors said on Friday.

Following a briefing by the secret services which took place behind closed doors on Friday, a member of the parliamentary intelligence committee said that Russia was involved in spying.

"Actions are being taken in respect of two agents of the Russian state," the lawmaker, Marek Biernacki told reporters.

"This was definitely a successful shot aimed at GRU," Biernacki said - a reference to the Russian military's Main Intelligence Directorate, which carries out covert operations.

Polish Deputy Prime Minister Janusz Piechocinski said in an interview with the TVN24 broadcaster that if it was true the men were spying for Russia, it would be a normal response for Warsaw to expel some Russian diplomats working in Poland.

On Friday, a Warsaw military court ordered that the officer, who was not named, be held in custody, also for three months, pending trial.