Kazakh state-run bank BTA has filed for protection from creditors in a Manhattan bankruptcy court after some of them took action against the lender which is restructuring $11.6 billion in debt.

Watched closely by foreign investors, the case is the biggest international debt restructuring in Kazakh history.

Once Kazakhstan's largest bank, BTA went into default last year shortly after the government took it over and accused its former managers of fraud -- a charge they have denied.

This petition is being filed at this stage as certain creditors have started to take action against the bank, BTA said in a Chapter 15 court filing.

For example, accounts of the Bank with UBS and Credit Suisse have been attached (had claims made against them) in Switzerland by a creditor of the Bank.

The court filing said Goldman Sachs had filed a complaint against BTA in a Russian court seeking judgment on what it described as an alleged 3.2 billion rouble ($104 million) claim on bonds issued by a special purpose vehicle and allegedly guaranteed by the bank.

BTA declined to comment on the filing.

The bank, which was nationalized last year to avoid collapse as a result of the credit crisis, has signed several preliminary agreements on restructuring but has yet to strike a final deal.

The bank said it maintains correspondent deposit accounts in New York to facilitate wire transfer and credit operations and the Chapter 15 filing would stop its creditors from taking action against its U.S. operations.

Market players say the move is in line with expectations but raises broader concerns with the protracted restructuring process.

There is growing market concern about the (restructuring) term sheet not being signed by the end of January as expected, said one industry source closely following the situation.

BTA was not immediately available to comment on the restructuring.

The case is In re: JSC BTA Bank, U.S. Bankruptcy Court Southern District of New York (Manhattan), No. 10-10638.

Kazakhstan has offered a stake in BTA to Russia's Sberbank once the Kazakh bank completes debt restructuring.

(Editing by Maria Golovnina and Jon Loades-Carter)