Takeover tensions around oil and gas play AWE Ltd have risen to fever pitch with the emergence of a potentially knockout $602 million all-cash offer from Japanese trader Mitsui and still some suggestions this third suitor may not be the last.

Mitsui's 95¢ a share offer easily trumps the $526 million deal the energy producer sealed with Mineral Resources before Christmas at 83¢ a share. It also eclipses the bid from China Energy Reserve and Chemicals Group at 73¢ a share that kicked off the takeover tussle but which is now well out of the running without a substantial increase.