CAIRO — Sudanese security forces tried again to break up an antigovernment sit-in outside military headquarters in the capital, Khartoum, killing at least 14 people Tuesday, activists behind the demonstration said.

The deaths brought the total number of fatalities in the sit-in since the weekend to 22, including five soldiers, according to the activists. The demonstration is the latest in nearly four months of protests that have plunged Sudan into turmoil. What initially erupted last year as rallies about the economy quickly escalated into calls for an end to President Omar al-Bashir’s 30-year rule.

On Monday leaders of the protests called on the military’s leadership to join their call for change. On Tuesday they invited military leaders to meet with their representatives to discuss arrangements for a transition.