(CNN) Sudan's ruling military council has called for an election after troops stormed the main camp of pro-democracy protestors and killed at least 35 people in a crackdown which has drawn international condemnation.

Hundreds were injured Monday in the capital Khartoum when the military tried to break up an opposition sit-in, according to the Central Committee of Sudan Doctors (CCSD), which is close to the protestors.

The demonstrators have demanded that the Transitional Military Council, which has ruled the country since troops ousted longtime President Omar al-Bashir in April, make way for a civilian-led interim body.

After the coup the military council and opposition groups agreed on a three-year transition to democracy. But in a broadcast early Tuesday, the council's leader Abdel Fattah al-Burhan called for national elections within nine months.

The only way to rule Sudan is through "the ballot box," al-Burhan said in an address on state TV.

He said the elections should be supervised by monitoring groups, including international and regional bodies. Al-Burhan said a caretaker government would be formed to oversee the period before elections.

Al-Burhan described those who died on Monday as "martyrs" and expressed "regret" at the violence, although he did not directly say military forces were responsible. He promised that Sudan's general prosecutor would investigate the incident and urged people to show a "spirit of forgiveness."

On Monday, Attorney General Maulana Al-Walid Sayed Ahmed Mahmoud announced that a committee had been created to investigate the incident.

Sudanese protesters close Street 60 with burning tyres and pavers as military forces tried to disperse the sit-in outside Khartoum's army headquarters on June 3.

Streets were quieter Tuesday, however the CCSD confirmed at least one death in Khartoum.

"One woman killed by stray bullet in her home in the Al-Deem neighbourhood," the group said in a statement.

They also noted that "there are several reports of deaths around Khartoum and in other province and we apologize sincerely for our inability to confirm or deny these [reports]."

The group added that it was difficult to confirm numbers because of the security situation, internet outages and the "pressure being put on doctors."

Internet blocks in place

The internet in Sudan is currently more severely restricted than it was during the removal of Bashir, according to monitoring organization Netblocks.

Since Monday, there have been blockages in place across all the country's major internet providers, although it is not a total outage.

"It appears some effort is being made to restrict selectively, either because those who ordered the disruptions also rely on some networks which need to be kept running, or because the network operators are not cooperating willingly," Netblocks said.

Sudanese forces are deployed around Khartoum's army headquarters on June 3 as they try to disperse Khartoum's sit-in.

What happened on Monday

There have been protests in Khartoum since the coup in April. The military has tried in the past to disperse demonstrators -- but on Monday it used live rounds, according to multiple eyewitnesses.

According to the Central Committee of Sudan Doctors, the casualties were caused by live bullets, and security forces surrounded hospitals where the wounded and the dead were taken.

A spokesman for the Transitional Council said the military "didn't disperse the sit-in by force" but that the security crackdown was instead focused on a gathering in a nearby "dangerous" area.

Video footage showed small fires and billowing smoke clouds, and protestors fleeing from audible gunshots. Protestors said they themselves were peaceful and unarmed.

Sudanese protesters gesture as smoke billows from burning tyres near Khartoum's army headquarters on June 3.

The UK's Foreign Secretary Jeremy Hunt, the British Ambassador in Khartoum, Irfan Siddiq, and the Assistant Secretary for the US Department of State's Bureau of African Affairs, Tibor Nagy, have all strongly criticised the violence.

United Nations Secretary-General António Guterres said he "strongly condemns the violence and reports of the excessive use of force by security personnel on civilians, that have resulted in the deaths and injury of many."

In a statement, Guterres' office added he "condemns the use of force to disperse the protestors at the sit-in site and he is alarmed by reports that security forces have opened fire inside medical facilities."