Hired buses transporting NASA supporters to Nairobi were on Monday night detained by police officers in Taita-Taveta County.
Several passengers without identity cards were arrested during the operation by armed police officers.
Three hired buses belonging to Modern Coast were flagged down at Maungu Township on Nairobi-Mombasa highway.
The Opposition supporters were travelling from Mombasa to Nairobi for the swearing-in ceremony of NASA leaders Raila Odinga and Kalonzo Musyoka.
According to the police, the three buses were defective and overloaded.
Thomas Abiero, one of the passengers, said 11 NASA supporters without identity cards were arrested and briefly detained before they were released.
Speaking to the Press at the Voi Police Station, the passengers alleged the operation was a strategy to prevent them from attending Raila's swearing-in.
The police, however, denied the allegations saying they would not have allowed the buses to proceed because they were faulty.
County Commissioner Kula Hache and Voi OCPD Joseph Chesire said the buses were intercepted at 1.30am.
Mr Chesire said the buses had one driver each, which was against the traffic laws.
“The buses had a broken screen and minor defects,” added the police officer.
Ms Hache, who is also the chairman of the county security committee, said the buses were detained due to traffic offences.
The buses were later released and the drivers took the passengers back to Mombasa.
Mohammed Amin, one of the drivers, said the buses were released after they paid a cash bail of Sh10, 000 each.
He said they would appear in court next week.
Amin, however, said the drivers had no idea where the passengers were heading to.
The drivers were roughed up by passengers after they declined to proceed with the journey to Nairobi.