The condition of the former Russian spy who was allegedly poisoned in London three weeks ago worsened overnight, the hospital said today.
A spokeswoman for University College Hospital in London said Mr Alexander Litvinenko (43) was now in a "very serious" condition and remained in intensive care.
The BBC reported that X-rays had shown he has apparently swallowed unusual objects.
A hospital source has told the BBC that three objects of dense matter lodged in his intestines were revealed. It is not clear whether the objects are the cause of his illness, and the hospital has refused to comment.
Police previously said Mr Litvinenko, was "deliberately" poisoned.
Mr Litvinenko a critic of Russian President Vladimir Putin, says he fell ill after meeting two Russians at a hotel.
He had been investigating the killing of Russian journalist Anna Politkovskaya, also a vocal critic of Mr Putin, who was shot at her Moscow apartment last month.