It also showed off two new smartphones, an updated Surface tablet and a new fitness band.

Much is riding on the launches as chief executive Satya Nadella sets out to prove Microsoft can compete with its rivals.

Analysts said the new laptop may help revive the ailing PC market.

The laptop, Microsoft's first, was the highlight of a tranche of new products shown off at an event in New York.

It is designed to take on Apple's Macbook, with Microsoft directly comparing the products.

It said that, just as its Surface tablet was a hybrid between a tablet and a laptop, so the Surface Book would "reinvent categories".

Analysts seemed impressed.

"It is a highly innovative, flagship device that will act as a much-needed halo product for Windows 10 and the broader PC market and proves that innovation in personal computing is not just confined to Apple's Cupertino campus," said Ben Wood, head of research at CCS Insight.

The device, which weighs 1.6lbs (0.7 kilograms) and is 7.7mm thick, comes with a touchscreen that can be separated from the keyboard. It will be available at the end of October for $1,499 (£984).

Microsoft

Microsoft also showed off two new smartphones - the 5.2in Lumia 950 ($549) and the slightly larger Lumia 950 XL ($649) both of which will be available in November.

Features include a 20 megapixel camera, a dedicated camera button, the ability to capture 4K video and 32 gigabytes of storage.

A cheaper Lumia 550 will be available in December, priced $139.

Mr Wood said Microsoft still had a "mountain to climb" to regain relevance in the smartphone market.

"These new Lumia devices tick all the boxes in terms of specifications and features but they are unlikely to be enough to lure customers away from the iPhone or Android-powered rivals," he said.

Microsoft also showed off its much-anticipated upgraded tablet - the Surface Pro 4 which will be released at the en of October, priced at $899.

It is thinner, with new screen technology, a more ergonomic keyboard cover and various other upgrades.

Mr Wood described it as "an impressive update".

Also on show was an updated fitness band, dubbed Band 2.

The wearable comes with a improved curved design and 11 sensors including a barometer to track elevation. It is linked to virtual assistant Cortana and the Microsoft Health platform, which will provide users with feedback on their fitness.

It will aggregate anonymised data from Band owners so that users can compare their performance with people of a similar age, weight and fitness.

Priced at $249, it will be available at the end of October.

Mr Wood said that the band showed that Microsoft remained "committed to the wearables category" but that the device was more "functional than fashionable".

(BBC)