Sweden's Sweco bids for Grontmij to build engineering consultancy leader

* Sweco (Stockholm: SWEC-A.ST - news) bids EUR 354 mln in combined cash and shares deal

* Sweco adds five new markets in Northern Europe

* Combined group would have sales around EUR 1.7 bln

* Sees (Shanghai: 600481.SS - news) synergies of EUR 27 mln (Adds detail, Sweco CEO comments, updates shares)

STOCKHOLM, June 1 (Reuters) - Sweden's Sweco said on Monday it was offering 354 million euros ($387.4 million) in a cash and shares deal for Netherlands' Grontmij N.V. in a move that would create Europe's largest engineering consultancy group.

The Swedish consulting company that operates in construction and environmental engineering, said the companies were a "near-perfect" geographical fit and estimated annual synergies and operational improvements of 27 million euros.

A transaction would make Holland, Belgium, Denmark, Germany and Great Britain new markets for Sweco, which currently only has 3 percent of its sales in European markets outside the Nordic states.

"We think that this part of Northern Europe fits us best to seize future growth opportunities. We believe mature markets in nearby countries are good for us," Sweco's Chief Executive Tomas Carlsson told Reuters.

He said the combined group would be the largest technical consultancy in Europe with sales of around 1.7 billion euros. Leading competitors include Britain's Atkins and Dutch Arcadis (Other OTC: ARCAY - news) .

The new group would have 14,500 employees, against Sweco's current 8,500.

The offer has been unanimously recommended by the Executive Board and the Supervisory Board of Grontmij and is supported by major shareholders of Grontmij representing 45 percent of the share capital.

Sweco said Grontmij's shareholders are being offered 1.84 euro in cash plus 0.22195 newly issued Sweco B shares for each share, representing a 22 percent premium over Grontmij's closing price on May 29.

Grontmij shares rose 15 percent on the news at 0810 GMT, while Sweco shed 0.4 percent. ($1 = 0.9138 euros) (Reporting by Oskar von Bahr, editing by Louise Heavens)