Facebook will test limiting the number of published news stories that can be read for free on its Instant Articles platform for premium publishers, U.S. media reported on Wednesday. The leading social network has become a major source of news for people, triggering complaints by publishers that they lose control and revenue when their stories are shared free at Facebook.

A paywall is under construction in Facebook's Instant Articles section where the social network has agreements with select outlets to publish directly to the platform, according to a story initially published online at TheStreet The service was launched two years ago and competes with Google's AMP that also optimizes content from select media for mobile web browsing.

Facebook head of news partnerships Campbell Brown said at a digital publishing conference in New York on Tuesday that the social network is responding to publishers' concerns with the move, TheStreet reported. Facebook in October will begin testing a feature that limits to 10 the number of stories that can be accessed in its "Instant Articles" section and guides readers to publisher home pages to consider buying subscriptions, according to media reports.