Facebook's bid to buy photo-sharing app Instagram for $1bn will be probed by the UK's Office of Fair Trading, according to the watchdog, which invited informal submissions of comment on Friday.

The dominant social network's takeover plan of Instagram has concerned the OFT, which is worried that the photo app market could be stifled if Facebook's acquisition completes.

The watchdog could refer Mark Zuckerberg's Instagram bid to Blighty's Competition Commission in late August. Before that, it is offering a window of just two weeks for interested parties to air their views to the OFT.

Separately, on the other side of the Atlantic, the Federal Trade Commission is also probing Facebook's planned buyout of Instagram to see if such a merger might deaden the air for other photo app players in that market.

In the US, the FTC automatically pokes at planned acquisitions valued at more than around $70m.

Facebook acknowledged the investigation and said it would "continue to work closely with the OFT and look forward to answering any questions that arise."

The Guardian reported that Facebook had already responded to the regulator's initial questions about the deal. But it's unclear if the OFT has jurisdiction over the proposed buyout.

The Register asked the OFT to comment on this story. It hadn't immediately got back to us at time of publication. ®