This comes after a suicide blast near Mogadishu airport, which is the site of the presidential election. Police sources say at least four people, including two security personnel, were killed and seven people were wounded.
More than 300 MPs will converge at the airport to vote for the president, who will govern for the next four years.
Key candidates in the elections include President Mohamed Abdullahi Farmajo and his two predecessors, Hassan Sheikh Mohamud and Sharif Sheikh Ahmed, who is widely regarded as front-runners.
The vote has witnessed a series of delays before a date was finally set for Sunday, May 15.