“We are aware of an explosion in the Eastleigh area. We do not know exactly what happened. At least five people have been reported injured. Police are currently heading to the scene to get more details,” Nairobi police chief Moses Nyakwama told AFP.
The blast, which occurred at around 7:30pm local time (1630GMT) reportedly happened near a supermarket in the predominantly Somali neighbourhood of Eastleigh, which has been the scene of deadly attacks recently.
Just last month at least seven people were killed and many more wounded in a bomb attack on a bus in the area.
Kenya has suffered a string of attacks often blamed on Al-Qaeda-linked Shebab militants since it sent its troops, now integrated into an African Union force, into Somalia.
The troops seized the Shebab bastion of Kismayo in September, a key southern Somali port, prompting warnings of retaliation from both the insurgents and their Kenyan supporters.