6.-- Facebook will begin selling video advertisements later this week, The Wall Street Journal reported, citing people familiar with the matter.

The ads will play automatically in users' news feeds. Facebook plans to make the announcement on Tuesday and the ads will begin on Thursday on users' feeds both on the Web and on smartphones, the people familiar with the matter told the Journal.

How long the ads will be is unknown, the Journal said. The newspaper previously reported Facebook planned to offer ads of up to 15 seconds on both smartphones and the Web.