Facebook Inc.’s U.S. visitor tally rose in June, the first increase in at least three months, while the average time spent by each user also gained, according to research released today by ComScore Inc.

In other news, the world’s biggest social-networking company, formed a partnership with Comcast Corp.-controlled NBCUniversal to provide coverage of the 2012 Olympic Games in London.

The number of U.S. unique visitors rose 1.1 percent to 159.8 million in June from May, following declines in each of the two preceding months, according to the Reston, Virginia- based researcher. Average time spent online increased 5.1 percent to 400.2 minutes, or more than six-and-a-half hours, after a gain of less than 1 percent the previous month.

Facebook (Nasdaq: FB), which held its initial public offering in May, is counting on continued growth in users and the time they spend on the site to boost demand for advertising. Most of Facebook’s revenue comes from spending on ads and about half of the total comes from the U.S. and Canada.

The owner of the world’s most popular social-networking service will release second-quarter results July 26, the first time since the Menlo Park, California-based company held its IPO in May.

The stock has struggled since its public debut at $38. Shares fell 1.6 percent today to close at $30.97, or 19 percent below the IPO price.

Olympics “Likes”

Facebook will host an NBC Olympics page with news, results, photo galleries, trivia and polls, NBC said today in a statement. Users who “like” the site will get exclusive content, according to the broadcaster, which said no money is changing hands in the deal. NBC Olympics introduced a timeline application on its website so Facebook friends can share content.

NBC’s coverage of the games will include a social-media segment featuring a daily poll and “Talk Meter,” a new Facebook data tool that will tell viewers what users are saying on the website about the Olympics. The games are scheduled to begin on July 27.

The partnership underscores the increasing ties between television and social media. In 2010, NBC began “Twitter Tracker” for the Vancouver winter games, which created a visual interface from messages, called tweets, about each sport.

“Social media is an important part of how fans consume and interact during the Olympics,” Gary Zenkel, president of NBC Olympics, said in the statement.