STOCKHOLM (Reuters) - The chief executive of SEB (SEBa.ST: Quote, Profile, Research) said on Tuesday the value of the Swedish bank's bond portfolio fell further during the first quarter as turmoil in global financial markets continued.

Annika Falkengren said the bank's liquidity and trading portfolios had continued to feel the effects of an international credit crunch that has caused some European and U.S. banks to write off billions of dollars in assets.

"Especially during March, credit spreads widened a lot because of market turbulence," she said at the bank's annual general meeting.

"That resulted in a further fall in the value of the bonds in our portfolio," she said.

Falkengren did not give a figure for how much the bond portfolio had lost but said spreads had widened nearly as much in the first quarter as in the second half of 2007.

However, she said the bank had outlined its credit holdings to investors in its third-quarter report and that there were no shocks waiting investors and analysts.

"We have been very transparent. I don't feel that we have any hidden or ugly securities in our portfolio," she said, repeating that 99.3 percent of the bank's debt holdings had high credit ratings.

In the fourth quarter, SEB took a mark-to-market writedown on its fixed-income portfolio of 990 million Swedish crowns ($167 million). In the previous quarter it took a 800 million crown writedown.

Rival Handeslbanken (SHBa.ST: Quote, Profile, Research) at the end of March warned investors of that its first-quarter earnings would include a 946 million crown writedown as the credit crunch slammed the value of its fixed-income holdings.

(Reporting by Simon Johnson and Eva Odefalk; Editing by Erica Billingham)