A male lion that strayed into rush hour traffic in the Kenyan capital on Friday injured one man before being captured and taken back to a reserve that lies on the edge of the city, the Kenya Wildlife Service (KWS) said.

KWS, which manages the country's safari reserves including the Nairobi National Park on the outskirts of the capital, said its units had caught the lion after images posted on social media showed it wandering along a main road near the park.

"A man who was injured by the lion (has been) taken to hospital," KWS said on its Twitter feed.

KWS spokesman Paul Udoto told Kenya's NTV that the elderly man was in a stable condition after the black-maned lion attacked him when it became agitated by the hooting of car horns by passing motorists.

The images on social media showed the lion walking along a grassy verge next to the busy road and past some people who looked on from behind a closed iron-bar gate.

Inside Nairobi National Park, which lies on the city limits, tourists enjoy views of lions, rhinos, giraffes, zebras and other wildlife against a backdrop of high-rise buildings.

Lions are occasionally spotted in the city close to the park after finding a way through fences that protect the built-up areas near the reserve.