Shares in Fannie Mae and Freddie Mac fell on Friday amid concerns foreign investors were reassessing their exposure to the troubled US mortgage financiers’ bonds and guaranteed securities.

Bank of China this week revealed it had cut its portfolio of securities issued or guaranteed by the two government-sponsored enterprises by a quarter, or $4.6bn, since the end of June. The sale underscored signs of nervousness among foreign buyers of Fannie and Freddie’s debt.