The organisers of the annual Heineken Open'er festival have confirmed two more top acts for this June's musical extravaganza.

U.K. indie outfit British Sea Power are set to join the festival, as are American rockers The Twilight Singers. The latter was founded by Afghan Whigs frontman Greg Dulli.

The new additions bolster an already impressive roster for this year's shindig. Pulp, Coldplay, The Strokes, Cut Copy, Kate Nash, The Wombats and Big Boi are amongst the acts already signed up to strut their stuff.

Heineken Open'er was launched in Warsaw in 2002, but the following year it moved to the coastal city of Gdynia, where it has remained ever since, evolving into a four-day-extravaganza.

Voted Best Major Festival at the European Festival Awards last year, the event has welcomed many of the hottest names in pop, rock, rap and dance, from Kanye West to The Kings of Leon to The Chemical Brothers.

This year's incarnation begins on 30 June. (nh)