Watch Replay of Today's Facebook Event on Instagram Video

NEW YORK (AP) — Facebook is adding video to its popular photo-sharing app Instagram, following in the heels of Twitter's growing video-sharing app, Vine.

Instagram co-founder Kevin Systrom said Thursday that users will be record and share 15-second clips by tapping a video icon in the app. They can also apply filters to videos to add contrast, make them black and white or different hues.

"This is the same Instagram we all know and love but it moves," he said at an event held at Facebook's Menlo Park, Calif., headquarters.

Vine, which launched in January, has 13 million users and lets people create and share 6-second video clips. Instagram has 100 million users, up from 20 million when Facebook bought the company more than a year ago. If users like it, Facebook's move could propel mobile video sharing into the mainstream.

Watch a replay of the Facebook event...

To use the video feature, Instagram users can tap on the same camera icon they use to snap photos. A new video camera icon will appear on the right side. Tap it and a screen with a red video button will let you record clips of sunsets, kids running in parks or co-workers staring at their computer screens.

The app will record as long as your finger is on the red button or for 15 seconds, whichever comes first. Not unlike Vine, taking your finger off the button will stop the recording, allowing you to shoot the scene from a different angle or record something else altogether. Once you have 15 seconds of footage, you can play it from the beginning and post it on Instagram to share with others.

Given Vine's popularity, "it is perhaps more surprising that Facebook has not introduced video for Instagram sooner. There is no doubt Twitter will move quickly to up the ante on Vine and this could undercut Facebook's efforts with video on Instagram," said Eden Zoller, principal consumer analyst at Ovum, a technology research firm, in an email.

Facebook Inc. initially agreed to pay $1 billion in stock for Instagram in April 2012, but the value had fallen to $715 million by the time the deal closed last August. Facebook still hasn't proven it will be able to make money from Instagram as it has not introduced ads on the service.