Mbeketoni eywitnesses say Al-Shabaab gunmen executed men in front of their families and killed others who had gathered to watch World Cup football on television.
"The attackers were so many and were all armed with guns. They entered the video hall where we were watching a World Cup match and shot indiscriminately at us," Meshack Kimani said, adding about 10 people were killed there.
"They targeted only men but I was lucky. I escaped by hiding behind the door," he said.
More top news
President is 'planing to overturn' guidance ordering schools to allow trans students to use the toilets matching their gender identity.
Republican politicians have faced a barrage of questions about the Trump administration's agenda during hostile town hall meetings.
An unemployed plasterer who admitted the one-punch manslaughter of banker Oliver Dearlove has been cleared of his murder.