Employees at French mobile carrier SFR took industrial action against the company's proposed break up, which could lead to thousands of jobs being lost.

After unions called for strikes earlier this month, an estimated 3,500 employees went on strike yesterday afternoon.

As reported by French newspaper Les Echos, workers gathered in front of SFR's parent company Altice France HQ yesterday to voice their concerns.

It comes months after Bouygues, Orange, and Free have struck an agreement worth €20.35 billion ($23.2bn) to acquire SFR's assets in France.

The trio put forward an offer of €20.35 billion ($23.66bn) to snap up SFR in April, which was an improvement on the previous one put forward to Altice Group in October, when Altice owner Patrick Drahi immediately rejected a €17bn ($19.8bn) offer from the consortium.

The terms of the deal remain the same, with Bouygues Telecom taking a 42 percent share, 31 percent for the Free–Iliad Group, and 27 percent for Orange.

However, the deal would see the French mobile operator market shrink to three from four, raising concerns around job security for SFR workers.

Reports noted that the purpose of the strike action, which was organized by the inter-union group made up of Unsa, CFDT, and CFTC, was to "make their concern, anger and determination heard" following the announcement of the deal back in June.

France 3 reports that a redundancy plan has been proposed to workers at SFR, which could see a total of 5,600 jobs cut of the 12,500 total jobs. This would represent more than 40 percent of the total workforce.

"If we take into account the scope of indirect jobs, because telecoms have a lot of subcontracting in engineering, in IT, it represents perhaps 12,000 employees in total," said François Monger, UNSA Saint-Herblain union delegate.

During the protests, there was particular anger shown to the consortium buying SFR, along with Altice France owner Patrick Drahi, as workers want assurances over their long-term futures at SFR, amid the proposed break-up of the business.

Further discussions are set to take place between the unions and the telcos in the coming weeks.