The galactic battle between laser cannon-toting aliens and the elite supersoldiers of UN Space Command spilled into British supermarkets this week as Halo Reach was released.

The multiples opened their doors at midnight on Tuesday to meet demand for the much-anticipated X-Box 360 video game, which sold 300,000 copies in first-day sales across the UK [UKIE/GfK-Chart Track].

On a global scale it clocked up $200m in 24 hours, making it the biggest entertainment launch of 2010, claimed Microsoft.

Tesco, Asda and Sainsbury’s kicked off a price war by undercutting high-street stores such as Game and HMV. The game has an rsp of £59.99, but was available for £34.99 at Sainsbury’s and £37.70 at Tesco. If Tesco shoppers also bought £17 of credit for the online gaming portal Xbox Live, the retailer offered an rsp of £28.

Asda priced the game at £37.47 but claimed its overall launch offering was “best in class” as it released a raft of extra Halo-themed PoS including a limited-edition Halo Reach hoodie (rsp: £9).

“It sets us apart from the rest of the market in terms of what we can offer,” said games buyer Alastair Islip. “The look and feel of our games department is clearly different from Tesco.”

In 2009, Asda’s overall gaming sales were more than 40% ahead of the total market, he added.

Tesco introduced Halo Reach-branded pallets for the launch and claimed unit sales were “in their thousands and had already exceeded expectations”.