A powerful earthquake has hit eastern Democratic Republic of Congo, near Lake Tanganyika and the Tanzanian border.
At least one child died after houses collapsed in the Congolese town of Kalemie, 55km north-west of the quake's epicentre.
The shocks were felt in Tanzania, Burundi and Rwanda, and by the Indian Ocean. Hundreds fled in panic from offices in the Kenyan capital.
The quake hit with a 6.8 magnitude at 1219GMT, the US Geological Survey said.
The epicentre was about 13km (8 miles) underground, the USGS said, some 975km (600 miles) south of Nairobi.
East Africa's Great Rift Valley runs along a geological fault line, but has largely escaped major quakes in recent years.
Three aftershocks were felt in Kalemie on Tuesday, reports the AFP news agency.
One aid worker told AP news agency on Monday evening that the injured were being taken to hospital.
"Dozens of houses have collapsed, several children were buried by the roofs of their houses," said Jean-Donne Owali by telephone from the lakeside town of Kalemie.
He said he saw children at one clinic bleeding from wounds to the head suffered when their mud-and-thatch homes collapsed on them.
Much of eastern DR Congo has been ravaged by war in recent years and is blighted by poor communications and infrastructure.
"There is quite a lot of damage to these poorly constructed houses," Michel Bonnardeaux, spokesman for the UN Office for the Coordination of Humanitarian Affairs in the DR Congo capital, Kinshasa, told Reuters news agency.
"Residents told us that some people had died and others were injured but we do not have any figures yet," he said.
Workers in Nairobi were quick to rush to safety when the quake hit
"A quake of this kind could easily produce significant damage, but I wonder what kind of infrastructure they have there in the region," said Dr Andrzej Kijko, head of seismology at South Africa's Council for Geoscience.
"There may not have been much to destroy."
The strength of the quake was reportedly felt in six countries, and prompted panic among some people working in Nairobi's high-rise offices.
Witnesses said that tremors lasted for about 15 seconds.
"People came running down - scared - because you don't know what it is. You're moving this way and that," Nairobi worker Tabitha Nyambati told Reuters.
Cracks appeared in some Nairobi buildings after the quake, witnesses said.
Reporters and witnesses said tremors had been felt in Rwanda's capital, Kigali, and in Bujumbura, capital of Burundi, as well as in DR Congo, Tanzania, Kenya and Uganda.
The following comments reflect the balance of opinion we have received:
Hi, just had a look at the map on the USGS site and the epicentre is in fact in Tanzania. It's on the Tanzanian side of Lake Tanganyika: Location 6.212°S, 29.599°E
Just past 3:15 p.m. I was driving in Town and was stationary due to traffic when suddenly I felt the car shake. Initially I thought of someone having banged into my car, but later on I saw many people running out of shops and offices shouting 'Earthquake!', that's when I realised. It was a huge tremor for everyone to feel and the ground upon which we stood to shake.
Sheetal Aggarwal, Arusha, Tanzania
Around 4pm, we were working in the office and witnessed a serious tremor. It continued for 5 minutes. We got panicked. Then the situation become normalised.
Syed, Kampala & Uganda
I was out, walking towards the front entrance of our office building, when I suddenly met a crowd of people running in panic. I thought it was a civil unrest situation and instinctively ran to an alternative rear entrance into our building. There, surprisingly, I met the occupants who didn't know what had happened. Now I realize how lucky we were, that it was not a powerful earthquake here in Nairobi, for running into a building is not what one does in such a situation. Those who were in the higher floors reported a dizzying shake that moved furniture items about. I just hope there are no casualties in the DRC, the epicentre of this quake.
Darlington Moshi, Nairobi, Kenya
I was in the office when we felt the tremors. There was a little bit of chaos on the stairs as everyone wanted to get down. It was very scary as we've never had this experience in Dar before. God bless us all.
Mili Ramaiya, Dar es Salaam, Tanzania
We evacuated our building in Luanda, after we felt it shake at about 13:25, local time and we're nearly 2500km away from the epicentre.
Matt, Luanda, Angola
It woke me up from a nap. The frame for the mosquito netting shook, and seemed to go on for about ten seconds. But my son, who was outside, did not feel it at all, even though we were 90 miles north of the epicentre.
Rebecca Sun, Kigoma, Tanzania
The quake caused some panic, but it appears not to have done any damage. A more serious quake in Kenya could have presented a severe challenge for Kenya right now, given that the President is yet to appoint a Cabinet.
Pete Ondeng, Nairobi
I'm currently working in Kampala and was on messenger with my girlfriend who lives in Arusha, 400km away on the other side of Lake Victoria. Suddenly, my office building started to rock gently, enough to move the chair I was sitting on a few inches over. Just as I started to tell my girlfriend what was happening, she wrote that her office was being evacuated due to an earth tremor. I do find it hilarious that offices were evacuated among some panic in Nairobi, 200km further away from the epicentre than Kampala and we didn't even think of moving (apart from me moving my chair back in front of my desk...)
Steve Hathorn, Kampala, Uganda
I was with my sister and a few customers here in the internet cafe, and I actually felt my chair rocking. It didn't bother me so much until someone next door came out running, shouting that it was an earthquake, but no body was hurt thank God.
Catherine Muwonge, Uganda, Kampala
I'm on the 12th floor of a building in the Central business district in Nairobi. The building swayed a bit. Pictures on the walls did not move. Office door swayed about an inch. A big deal of nothing for someone, like me, who has lived through a lot more in California.
Neil Ribeiro, Nairobi, Kenya
Yes we all felt the tremor - long one for sure but no damage around in the north Katanga despite the reported intensity of the earthquake. Only some huts have been reported damaged.
Rajeev, Kalemie, DRC
The earthquake was also felt in Kigali at the same hour, I could see the bookshelves, and the fun in my office shaking. My colleagues in the next office felt the same. There are no reports of casualty or any other damage on buildings.
Theo Rwigema, Kigali, Rwanda
I think it's scary that a quake could hit East Africa as this is not a very active earthquake zone. I'm very surprised and shocked that those tremors were actually from an Earthquake!
Dr Andrzej Kijko, South African Council for Geoscience: "There may not have been much to destroy." His comments are hurting. Has he ever come to this region? Human lives are the most precious and important. Let him know we value each other in this region and it is very sad for a learned person to talk ignorantly he should apologise to the people of this region.
Faith Njoroge, Kenya, Nairobi
Will that Dr Kijko from South Africa get real? There is enough infrastructure in Nairobi that could be destroyed, I mean with all his education he should know better! And the tremor only lasted for a few seconds here in Nairobi and nothing was damaged stop being so dramatic!
I sincerely sympathise with my fellow Africans in the affected areas as they cope with this natural disaster. May God comfort them. I hope all necessary logistics are in place to help the wounded and displaced.
Omorodion Osula, Boston, USA