A Sudanese medical union says at least one person has been shot dead by security forces near a sit-in outside the military's headquarters in the capital, Khartoum.

The Sudan Doctors Committee says the shooting took place late Saturday on Nile Street and that at least 11 people were wounded.

Two people were killed in the area last week.

The doctors committee is part of the Sudanese Professionals Association, which has been spearheading the protests that led to the military overthrow of longtime ruler Omar al-Bashir in April.

Tens of thousands have staged a sit-in outside the military headquarters since April 6, following nearly four months of protests against al-Bashir.

Tensions have risen as negotiations remain deadlocked between protesters and the generals, who took over the country after al-Bashir's ouster.