French conglomerate Bouygues, active in construction, real estate, media and telecommunications, said on Tuesday its half-year profit tumbled 29 percent on problems in its telecom unit. The company said net profit dropped to 278 million euros ($349 million), while analysts polled by Dow Jones Newswires had forecast 391 million euros in earnings over the January to June period. Operating profit in the first six months of the year fell back 37 percent from a year earlier, hit by poor results in its telecom unit Bouygues Telecom, but overall sales rose by 2.0 percent to 15.5 billion euros. Until recently Bouygues Telecom was a company cash cow, but profit at the unit tumbled by 57 percent in the first half as the company fought hard to keep customers lured away by low cost competitor Free Mobile. \"Bouygues Telecom is facing deep-seated changes on the mobile market, significantly denting its financial performance,\" the company said. A voluntary redundancy plan concerning 556 employees was proposed in early July, it said.