The head office of Linklaters' South African ally Webber Wentzel has been raided by police, with documents and equipment seized amid a dispute involving one of the firm's clients.

The Johannesburg office of Webber Wentzel – which has had an alliance with the magic circle firm since 2013 – was raided by the Hawks, South Africa's economic crime unit, earlier this month.

A Webber spokesperson confirmed that the Hawks arrived at its office on 1 June with a warrant to seize documents "in relation to allegations made against a client in an ongoing commercial litigation case".

The spokesperson added: "We are reviewing the lawfulness of the warrant and its execution by the Hawks on various grounds, including legal privilege. We ensured that the documents and information taken were sealed and will be kept by an independent third party, nominated by us, pending the outcome of an application to the High Court.

"We will ensure that our client's rights are protected and that legal privilege, which is a key principle to our profession, is upheld."

The client in question is South African telecoms company MTN, which is embroiled in a decade-long battle with Turkish mobile phone operator Turkcell over phone service provision in Iran. MTN's offices were also raided by the Hawks on the same day.

Webber is one of the 'Big Five' law firms in South Africa, the collective term for the country's top firms. It has two domestic offices, in Johannesburg and Cape Town, employs about 750 people and is led by managing partner Sally Hutton.

Its exclusive alliance with Linklaters, which reached its fifth anniversary earlier this year, does not involve any sharing of profits or revenues, but the pair do share a number of key clients including mining giant Anglo-American, and the South African firm prominently carries Linklaters' branding.

Linklaters also benefits from Webber's membership of the Africa Legal Network, which was founded by Kenyan law firm Anjarwalla & Khanna, and has law firm members in Botswana, Burundi, Ethiopia, Kenya, Mauritius, Mozambique, Rwanda, Tanzania, Uganda and Zambia.

Linklaters declined to comment.