DA members arrested ahead of Sona

Shaun August and Marius Redelinghuys were among those who were arrested.

A photo taken by Marius Redelinghuys from the inside of a police van.

CAPE TOWN - Four members of the Democratic Alliance (DA) were arrested in Adderley Street near Parliament during a gathering by its supporters ahead of the State of the Nation Address (Sona).

Adderley Street is part of the route President Jacob Zuma would take to make his speech. It's an area which has been turned into what the police have termed a "sterile zone" with lots of bars and railings set up along the pavement blocking off exits to the road itself.

DA supporters being arrested #SOna2015 RT @zakmbhele: Shaun August being led away and taken into custody. pic.twitter.com/uF1wfue9OC

Speaking to Eyewitness News from the back of a police van Redelinghuys said he still did not know why he had been detained.

"I was arrested after I had been assigned as one of the DA's members who had gathered along Adderley Street and who were being forcefully removed by the riot police. I have attempted to enquire with the police why they were being removed."

In a police lock up van for asking why @DA_News members were being shoved away from Adderley Street. Picture: Marius Redelinghuys via Twitter.

Phumzile van Damme has described the use of force by police as extreme.

Forceful arrest of DA Cape Town Metro Chair Shaun August caught on video RT @zilevandamme: pic.twitter.com/jmf1dm7QzZ #SONA2015

Reports also say a water cannon was used to disperse supporters.