Somalia’s opposition supporters and security forces clashed in the capital, Mogadishu, on Thursday for a second day ahead of a planned anti-government demonstration.

No official casualty figures were immediately available from the violence that prompted calls for restraint from the United Nations and the United States as the government and opposition traded blame for the violence.

Residents reported heavy gunfire and explosions as fighting broke out in several neighbourhoods Wednesday.

“We heard heavy weapons fire, and people were fleeing their homes,” said Abdullahi Mohamed, who lives in the city’s Howlwadaag district. “Many families left the area looking for safer places.”

The clashes underscore growing political tensions as disputes over Somalia’s elections and the constitution have increasingly strained relations between the government and opposition leaders. Somalia is also fighting al-Shabaab militants while seeking to strengthen state institutions with support from international partners.

Several buildings were hit by heavy gunfire and mortar shells during the clashes, with some catching fire.

Gunfire subsided on Thursday afternoon following mediation efforts led by the director of the National Intelligence and Security Agency, who visited the area and held talks with former Prime Minister Hassan Ali Khaire. The discussions reportedly led to an agreement to halt the fighting.

Opposition figures say the rally planned for later on Thursday was intended to protest what they call constitutional violations and efforts by President Hassan Sheikh Mohamud to extend his tenure. The government has rejected those allegations.

On Thursday morning, there were signs of mobilisation on the streets, but a heavy security presence remained in place with police patrolling major roads.

Mogadishu police said the violence stemmed from “organised attacks” carried out by armed militias.

“The incidents were not the organisation of peaceful public demonstrations, but rather coordinated armed acts that directly threatened the security, order and stability of the capital,” the police said in a statement.

State security forces repelled attacks on their positions and launched investigations to identify those responsible for organising, financing and carrying out the violence, police said.

Opposition leaders accused security forces of attacking residences linked to former Prime Minister Khaire and former President Sheikh Sharif Sheikh Ahmed.

“We are under attack,” Khaire said in a statement. “For the second time in less than 24 hours, Hassan Sheikh Mohamud has directed armed forces against our peaceful gatherings.”

Traditional elders, politicians and community leaders were meeting at Khaire’s residence when the attack occurred, he said. The government disputed that account.

The UN expressed alarm over the clashes. Secretary-General António Guterres said the violence resulted in deaths, injuries to civilians, and damage to critical infrastructure.

“The Secretary-General strongly condemns all acts of violence and incitement to violence undertaken for political advantage,” he said in a statement. Guterres also called on all parties to exercise restraint, protect civilians and resolve political differences through dialogue.

The US also voiced concern over the fighting. The US Embassy in Mogadishu described the violence as “reckless” and urged Somali leaders to seek a peaceful resolution.

“Somali leaders on all sides have a responsibility to preserve stability and resolve differences through peaceful means,” the embassy said. “Actions taken in the coming hours and days may have lasting consequences for Somalia’s security, unity and future.”

Khaire accused Mohamud of deploying state security forces against political opponents and alleged that troops trained and equipped by international partners to fight the al-Shabaab extremist group had been used against opposition figures.

• An AP report