– Plunging further into the world of online video, Facebook Inc. on Thursday unveiled a new video feature for its Instagram photo-sharing service.

The new feature lets users share 15-second video clips, according to Instagram Chief Executive Kevin Systrom, who called the app “everything we know and love about Instagram, but it moves.”

Facebook and Instagram have reportedly been working on developing a new video service for months, and the pressure to enter that market has increased since rival Twitter Inc. acquired the video-sharing application Vine last fall. Vine has caught on with many teens as well as celebrities who like the idea of creating short, often jokey, video clips and sharing them with friends.

Online video is also seen as a powerful new way to deliver advertising. While the Vine app is not believed to be a big moneymaker for Twitter, Google has shown that it can reap significant revenue from ads on its YouTube site. Recent research projected that U.S. advertisers will spend $4 billion on digital video ads this year, doubling to $8 billion by 2016.

Systrom, however, said there are no immediate plans to offer advertising with the new video-sharing feature.

“Over time, we’ll figure out how advertising ends up being OK on Instagram in a useful way,” he said, but added that the service for now will simply let commercial brands create their own video clips and share them “organically.”

The Instagram co-founder also pledged that the service won’t take videos and incorporate them into advertising. “We have no plans to use [your] photos and videos in any kind of advertisements,” he said.

Systrom acknowledged the recent explosion of video-sharing apps, but denied that was the reason for Instagram adding video now. He said Instagram had originally thought about sharing photos and video when the service was developed three years ago, but technology at that time didn’t allow fast and simple video-sharing.

Instagram is offering the new video service for both iPhones and Android smartphones. Users will be able to choose from 13 optional “filters” that alter the appearance of their videos, in a manner similar to the filters that Instagram offers for still photos.