The number of people killed since security forces stormed a protest camp outside the Sudan Defence Ministry in central Khartoum two days ago has risen significantly to 60.
This was confirmed on Wednesday by a doctors group linked to the opposition.
The death toll had earlier been put at 35.
Talks between the Transitional Military Council, which has ruled since President Omar al-Bashir was overthrown in April, and the opposition have ground to a halt amid deep differences over who would lead a three-year transition to democracy.
Kenya had cancelled all fights to and from the war torn nation.