Months of political tensions over the holding of elections in the fragile Horn of Africa nation have burst into the open, prompting the United Nations to call for "calm and restraint."
Gunfire has been reported in Mogadishu as the opposition tried to march against delayed elections in the Somali capital where roads have been sealed off and heavy security deployed over the planned protest.
Somalia missed a deadline to hold an election by February 8, when President Mohamed Abdullahi Mohamed, better known by his nickname Farmajo, was due to step down, creating a constitutional crisis.
Farmajo and leaders of the country's federal states have been unable to resolve squabbles over how the vote is to be conducted, after hopes of hosting Somalia's first one-person, one-vote ballot since 1969 were abandoned over security and political problems.
A coalition of opposition candidates has said they no longer recognise Farmajo as president and had vowed mass protests until he steps down, to begin on Friday.
A small group of protesters attempted to march down the main airport road when the shooting started.
It was unclear who opened fire first, but one witness Yusuf Mohamed reported a "heavy exchange of gunfire" between security forces and armed guards protecting opposition supporters.
"There can be casualties but we are taking cover now I don't know exactly what happened," he told AFP.
Meanwhile, witnesses and police confirmed an explosive projectile had hit an area hosting shops and restaurants just inside the airport gates, however it was unclear what it was.
"Something hit a restaurant inside the airport, it burned, I cannot say what it was but it caused a heavy explosion and fire that devastated the whole restaurant," said witness Liban Ali.
After the incident the opposition leaders addressed a press conference, charging the shooting incident was an assassination attempt and that rockets had been fired.
"Myself, several other candidates, legislators and other protesting civilians survived a direct attempt to get rid of us," said former prime minister Hassan Ali Khaire.
"If there was anyone with doubt about the dictatorship political ideology of Farmajo, they can get inspiration from what happened last night and this morning."
Another opposition leader, Abdiharman Abdishakur, said, "The rockets they fired at us passed and struck the airport where it caused destruction."
By early afternoon gunfire had subsided in the capital.
READ MORE: Bomb blast injures several near Somalia's presidential palace
The government had warned the opposition against staging the protest, due to soaring cases of coronavirus in the city. However, the opposition coalition vowed to press on.
The group is allied against Farmajo but includes candidates running individually for his job, including two of Somalia's former presidents.
Farmajo was due to hold a meeting with regional leaders on Mogadishu on Friday in the latest bid to resolve the election impasse.
Tensions first erupted overnight, with both sides accusing the other of staging attacks.
The Somali government in a statement accused "armed militiamen" protecting opposition leaders of attacking a government security checkpoint and seeking to take over parts of Mogadishu.
The opposition denied this and accused government forces of attacking the hotel where they were staying.
"They have attacked Maida hotel where myself and former president Hassan Sheikh Mohamud," were staying, said another former president Sharif Sheikh Ahmed on Twitter.
After the fighting overnight, government forces took control of the public square where the protest was to be held, and closed down all roads leading there, stationing military vehicles and troops around the capital.
The UN in Somalia (UNSOM) wrote on Twitter it was "deeply concerned by armed clashes in Mogadishu overnight and on Friday morning, calls for calm and restraint by all parties involved, and urges that open lines of communication be maintained to help reduce tensions."
1/2) The @UN in #Somalia is deeply concerned by armed clashes in #Mogadishu overnight and on Friday morning, calls for calm and restraint by all parties involved, and urges that open lines of communication be maintained to help reduce tensions. pic.twitter.com/4zhcuDnqxO— UNSOM (@UNSomalia) February 19, 2021
UNSOM highlighted the urgent need for the federal government and states to "reach political agreement" on the election.
Somalia has not had an effective central government since the collapse of Siad Barre's military regime in 1991, which led to decades of civil war and lawlessness fuelled by clan conflicts.
The country also still battles the Al Qaeda-linked Al Shabab militant group, which controlled the capital until 2011, but retains parts of the countryside and carries out attacks against government, military and civilian targets, seemingly at will, in Mogadishu and regional towns.
Somalia still operates under an interim constitution and its institutions, such as the army, remain rudimentary, backed up with international support.
The election was to follow a complex indirect system used in the past in which special delegates chosen by Somalia's myriad clan elders pick lawmakers, who in turn choose the president.
READ MORE: Political turmoil in Somalia leaves power vacuum