British insurer Aviva said it had temprarily frozen withdrawals from one of its property funds, blaming the increasing length of time it is taking to sell property assets.

The move means that investors in the Norwich Union Unit-Linked Property Fund (Life and Pensions) wishing to withdraw their cash will be unable to do so for up to six months, Aviva said in a statement.

"This action is in the best interests of investors by protecting the long term value of their investment and avoiding having to sell properties below their market value," Norwich Union marketing director David Barral said in a statement.

The fund is available to holders of Aviva's life and pension policies, and had assets under management of 2.9 billion pounds ($4.02 billion) at the end of 2008, an Aviva spokesman said.

Aviva's other property funds, including the Aviva Investors Property Trust, continue to trade normally, the company said.- Reuters