Instagram has began letting users easily tune into hot topics of the moment in a move that moves the Facebook-owned image sharing service squarely into Twitter's domain.

Updated versions of Instagram applications released in the United States for mobile devices powered by Apple or Android software boasted Explore pages complete with trending topics and places.

"The new Explore now surfaces trends as they emerge in real-time, connecting you to events and conversations both near you and around the globe," the Instagram team said in a blog post.

"We'll work to bring it to the rest of the world after we fine-tune the experience and set it up to work well in other countries."

More than 70 million photos and videos are posted daily on Instagram, making it likely there will be imagery related to attention-grabbing events, according to the service.

Twitter rose to prominence on its service that lets people share pictures, video snippets, and comments about happenings or hot topics in real time.

Instagram said that Explore pages will feature curated collections from "interesting accounts" such as those of musicians or extreme athletes or focused on potentially compelling places.

Search has undergone a "dramatic" upgrade in the latest version of the application, according to Instagram.

The challenge to Twitter came as the one-to-many messaging service based in San Francisco searched for a new chief executive capable of spurring both growth and revenue.

Twitter said on Monday that it would only consider chief executive candidates who can commit full-time to the company, signalling that co-founder and interim head Jack Dorsey likely will not be picked.

Dorsey, in addition to stepping in for outgoing Twitter CEO Dick Costolo, leads Square, a growing mobile payments company.

"The search is proceeding with a sense of urgency but the committee will take the time necessary to find the right CEO to lead the next phase of Twitter's growth," Twitter said in a released statement.