Activist investor Elliott takes stake in UK takeover target WS Atkins

* Elliott holds 6.8 pct stake -regulatory filing

* Position taken day after SNC Lavalin agreed to buy WS Atkins

* Elliott declines to comment on move (Adds SNC declines to comment )

By Vikram Subhedar and Simon Jessop

LONDON, April 24 (Reuters) - U.S. activist investor Elliott Capital Advisors disclosed on Monday it has taken a 6.8 percent stake in WS Atkins (Frankfurt: 912859 - news) after the British engineering and construction consultancy firm agreed to be bought in a C$3.6 billion ($2.7 billion) deal.

Elliott said in a regulatory filing that it acquired the stake in a contracts-for-difference deal on April 21, the day after Atkins agreed to be acquired by Canadian construction and engineering group SNC Lavalin.

Shares (Berlin: DI6.BE - news) in Atkins closed on Monday at 2,100 pence, above SNC (Shenzhen: 002246.SZ - news) 's offer price of 2,080 pence a share.

After SNC made an indicative offer for Atkins on April 3, Liberum analyst Joe Brent said in a note that the move could spark a bidding war, given growing consolidation in the industry. He declined to comment on Monday.

The stake in Atkins opens up another front in Europe for Elliott, as it presses Dutch-based paintmaker Akzo Nobel (Amsterdam: AKZA.AS - news) to open takeover talks with U.S. suitor PPG Industries (NYSE: PPG - news) , and separately campaigns for a restructuring at Anglo-Australian miner BHP Billiton (NYSE: BBL - news) .

Elliott's stake in Atkins makes it the second-biggest shareholder, Thomson Reuters (Dusseldorf: TOC.DU - news) data showed, just behind asset manager Columbia Threadneedle.

A spokeswoman for Elliott declined to comment on why the firm had taken a stake in Atkins. Spokesmen for Atkins and for SNC also declined to comment. ($1 = 1.3482 Canadian dollars) (Additional reporting by Justin Varghese and Esha Vaish in Bangalore and Allison Lampert in Montreal; Editing by Greg Mahlich)