Prices on the Karachi Stock Exchange have fallen sharply on the first day of trading since Pakistan carried out its nuclear weapons tests last week.

The main index was down more than twelve per cent by the close of trading.

Correspondents say the fall reflects uncertainty among investors over the effects of international sanctions against Pakistan for following India in exploding nuclear devices.

The Pakistan government had closed the Stock Exchange and issued emergency regulations -- including a freeze on foreign currency accounts and transactions -- after the first nuclear blast last Thursday.