Punch reported that the wounded citizen was taken to a clinic at the Federal Secretariat Complex, a few kilometres from the scene of the incident.
But the extent of his injuries could not be immediately ascertained.
The coalition members were having their sit-out at the Millennium park opposite the Unity Fountain, Maitama, Abuja when the armed policemen fired tear gas canisters to disperse them.
The participants, however, braved the assault and continued with their meeting for about an hour.
The protesters who are members of about four civil society organizations were demanding that Buhari should return to the country or resign if he was incapacitated.