Microsoft and Nokia joined Wednesday to boost their arsenal in the smartphone wars with two new Windows-powered devices aimed at battling Apple's iPhone and rivals powered by Google's Android system.

The new Nokia Lumia 820 and 920 are part of the Finnish-based company's strategy of offering "an alternative to the faceless black and grey monoblocs that you see out there," said Nokia president and chief executive Stephen Elop at a New York launch event.

"This is Lumia, the world's most innovative smartphone," Elop said in unveiling the two new devices powered by the Windows Phone 8 operating system.

Microsoft chief executive Steve Ballmer also appeared at the event, which offered no specifics on launch dates or prices in various markets.

"This is a very important milestone. It is unbelievable how far we have come in 18 months working with Nokia," Ballmer said.

Ballmer added that the launch highlights "the broader context of where we're going overall with Windows," with the launch of the new Windows 8 platform and Windows Phone 8.

"This is a year for Windows," he said. "Windows phones, Windows tablets, Windows PCs -- we've reimagined Windows from the ground up."

Offered in several bright colors such as yellow and lipstick red, the devices come into a sizzling market for smartphones now dominated by Apple and Android phones.

Nokia smart devices team leader Jo Harlow said the Lumia 920, which will be the new flagship, "is the most innovative smartphone in the world."

She said the phone has the most advanced camera of any smartphone, extended battery life and a display with "better than HD resolution."

"The clarity is so incredible that video just pops right out of the screen," she said.

The device also includes Nokia's location platform, which allows users notably to point the phone at a location in a city and get information on local shops and restaurants.

Harlow called this "the most intuitive way to explore the world around you."

The new phone's battery, she said, would be 30 percent more efficient than its rivals and also incorporate wireless charging, with Nokia joining an effort to bring this technology to airports, coffee shops and other locations.

The event also unveiled a Lumia 820, described as "a stylish, mid-range smartphone that delivers high-end performance in a compact package" with interchangeable shells, including one in purple.

Nokia's share price slumped more than 10 percent, but analysts offered a generally favorable view of the phones.

"It's definitely a step in the right direction," said Ramon Llamas of the research firm IDC.

"They are addressing some of the pain points for smartphone users like blurry and shaky pictures."

But Llamas said it will be a tough market in the fourth quarter with Apple expected to launch a new iPhone, and others also introducing new devices.

"Lumia is not the only thing out there," he said. "Some of the innovation they have is awesome but if they can't get the message out properly it's going to be novelty ware."

Michael Gartenberg of Gartner offered a similar view.

"Clearly Nokia has created a product that no one is going to confuse with anything else," he said.

"Now they have to execute and tell the story."

Gartenberg said the market is growing fast enough "to support multiple ecosystems" but that Nokia needs "to explain to consumers why different is better."

The signs of tough competition were underscored just hours later and a few blocks away in New York when Motorola Mobility, now owned by Google, unveiled three new Android-powered smartphones.

Nokia, once the leader in mobile phones, has been losing market share as consumers move to smartphones powered by Apple's iOS or Google's Android operating system.

The Finnish company's new strategy is phasing out its Symbian smartphones in favor of a partnership with Microsoft.

That alliance has produced a first line of Lumia smartphones, which Nokia is counting on to help it survive in a rapidly changing landscape.

The launch comes with Nokia losing ground and Microsoft holding only a modest share of the sizzling smartphone market.

According to Gartner, Android held a 64 percent share of the smartphone market in the second quarter to 18.8 percent for Apple. But analysts see Apple regaining traction with the launch of its new iPhone later this month.