By Kenneth Kiesnoski

PASSAU, Germany — Viking River Cruises, responding to market demand, said it will launch two additional vessels in 2012.The Embla and the Aegir will be part of the new Viking Longship class, bringing the total of such ships to debut next year to six.

The new vessels will be introduced in July and August 2012, joining the previously announced Freya, Idun, Njord and Odin, all to enter service in March.

“Ever since we announced the introduction of the Viking Longships earlier this year, the response has been overwhelming,” CEO Torstein Hagen said in a statement. “To accommodate demand, we have decided to accelerate the newbuild schedule.”

The two new ships are part of Viking’s $250 million fleet-redevelopment program, which includes refurbishment of existing vessels as well as the introduction of 10 Longships by 2014.

The Longships will measure 443 feet long and feature 95 staterooms, including two 445-square-foot Explorer suites; seven 275-square-foot Veranda suites; and 39 Veranda staterooms measuring 205 square feet.

The vessels will also have Viking’s new Aquavit Terrace, an indoor-outdoor lounge space; al fresco dining on the ship’s upper decks; and green features such as energy-efficient hybrid engines, solar panels and organic herb gardens.