Canadian oil giant Suncor Energy launched Monday an unsolicited $4.3 billion (US$3.3 billion) all-stock offer for oil sands producer Canadian Oil Sands.
Suncor's takeover move comes amid consolidation in the oil sands industry in western Canada, hammered by the fall in oil prices.
Canadian Oil Sands's share price shot up almost 50 percent in morning trading following the takeover bid.
Under the terms of the offer, shareholders in Canadian Oil Sands will receive 0.25 of a Suncor share for each COS share. Suncor said that represents a 43 percent premium based on the closing prices of the COS shares and the Suncor shares on Friday.
The offer includes assumption of an estimated $2.3 billion COS net debt, bringing the total transaction value to about $6.6 billion, Suncor said.
"We believe this is a financially compelling opportunity for COS shareholders," said Steve Williams, Suncor's president and chief executive, in a statement.
"By accepting this offer, COS shareholders will become investors in Canada's leading integrated energy company with 50 years of experience in oil sands operations and a track record of returning significant value to shareholders."
There was no immediate comment from Canadian Oil Sands.
Canadian Oil Sands holds the largest share in the Syncrude project, a massive producer of light, sweet synthetic oil from Canada's oil sands, which hold combined proven and estimated reserves of 4.4 billion barrels of oil. COS's share is 1.6 billion barrels.
Suncor's offer for Canadian Oil Sands expires on December 4.