Penn and Johansson 'together at wedding'

Sean Penn and Scarlett Johansson have added more weight to rumours they are an item after attending Reese Witherspoon's wedding together.

Penn, 50, and 26-year-old Johansson — who is a client of Witherspoon's agent husband Jim Toth — surprised the crowd of A-listers at the wedding by appearing together, according to entertainment website Popeater.com.

"Scarlett is Jim's client, but no one, including the bride, knew she would have turned up with Sean Penn," an unnamed friend of Johansson's was quoted as saying.

"Turning up at a wedding with your boyfriend is definitely a huge statement, especially that wedding."

Witherspoon married Toth on the weekend in a private ceremony at her Californian ranch.

Also in attendance were Robert Downey Jnr, Renee Zellweger and Spiderman star Tobey Maguire.

Penn and Johansson first kicked the rumour mill into overdrive when they were spotted at party in Los Angeles earlier this year for the movie Black Swan.

The pair has also been seen eating together and apparently jetted down to Mexico for a day trip.

Penn divorced wife Robin Wright in July last year after 14 years of marriage, while Johansson filed for divorce from actor Ryan Reynolds in December.