* Kazakhstan's pensions fund bought IBA bonds worth $250 mln
* Decision to buy bonds is "raising questions" - cenbank
* Kazakh central bank has exposure to IBA - former governor (Adds details, background, quotes)
By Mariya Gordeyeva
ALMATY, May 24 (Reuters) - Kazakhstan's central bank will investigate the acquisition by the state-managed pension fund of $250 million worth of bonds in the International Bank of Azerbaijan (IBA) after the lender announced it would not repay some of its debts in full.
The state-owned bank, Azerbaijan's largest, has suspended payments on some liabilities and is seeking support from creditors to restructure more than $3 billion of debt.
Some debt holders voiced anger on Wednesday after a meeting with Azeri officials in London at which they were told some would have to suffer losses under the restructuring plan.
The bank ran into problems in 2015 when bad loans built up. Azeri President Ilham Aliyev, on International Monetary Fund advice, ordered its balance sheet be cleaned up and the bank sold off, but no sale has occurred. The government has already taken over $5 billion in bad loans from IBA.
Kazakhstan is a close political ally of Azerbaijan. That Kazakh officials are now questioning the prudence of holding IBA liabilities is likely to add to the pressure on the Azeri state to implement the lender's restructuring.
Kazakh central bank head Daniyar Akishev said central bank officials took a decision in October 2014 to acquire, via an offshore company and a closed subscription, IBA's 10-year bonds with a coupon paying 8.25 percent annually.
"Some details related to these bonds purchase are raising questions, so the central bank, after conducting the internal checks, is going to send information on the pension fund's investments into the IBA papers to the related authorities for legal assessment," Akishev said.
Kazakh President Nursultan Nazarbayev has been informed of the situation, the central banker said.
A Reuters reporter at the IBA meeting with debt holders in London on Tuesday saw Kairat Kelimbetov, who served as central bank governor of Kazakhstan from October 2013 to November 2015, at the event.
Asked why he was there, Kelimbetov said he was with a Kazakh central bank delegation that was attending because the bank had exposure to the Azeri lender.
According to the restructuring proposal, IBA creditors have three options: the first involves swapping the debt into sovereign bonds with a 12-year maturity but amortising in three annual instalments in years 10, 11 and 12.
These would carry a 5.125 percent rate and with an "enhancement value" - or haircut - priced at 20 cents in the dollar.
The second option involved a one-on-one swap into 15-year 3.5 percent sovereign bonds, while the third option is to stay with IBA, with bonds exchanged at par for a 7-year 3.5 percent issue.
Akishev said that the central bank is taking measures to limit negative consequences from the restructuring and is in talks with IBA.
"Together with the government we will choose the most secure restructuring option, from the risk point of view. However, all three options assume a loss and lost profit," Akishev said.
Net assets of the state pension fund of Kazakhstan, a Central Asian nation of 18 million, were at 6.8 trillion tenge ($22 billion) as of April 1.
Around 9 percent were invested into non-Kazakhstan sovereign debt papers, with some 3 percent of that exposure to non-Kazakh private companies' papers such as bonds.
$1 = 311.0800 tenge Additional reporting by Sujata Rao in LONDON; Writing by Dmitry Solovyov and Katya Golubkova; Editing by Christian Lowe and Raissa Kasolowsky