Ticket-demand for Van Halen [ tickets ]'s first tour in almost a decade with singer Sammy Hagar [ tickets ] has led to additional nights in several markets.

Shortly after tickets hit the box office on Saturday (4/3), the group posted sellouts in Worcester, MA; East Rutherford, NJ; St. Louis; and Las Vegas. Tickets are on sale now for second performances in each of the aforementioned cities.

Tickets for the first date at Las Vegas's Mandalay Bay Events Center sold out in less than 30 minutes, making it the fastest sellout in the venue's five-year history, according to a press release.

The band has also added to its itinerary an Aug. 16 performance in Anaheim, CA, and moved its previously announced stop in Washington, DC, from June 28 to June 25; previously announced stops in Hartford, CT, and Albany, NY, no longer appear on the group's schedule.

Tickets for about half of the band's confirmed tour dates are on sale now. The group is also offering special ticket packages through iloveallaccess.com. More information is available at the group's website.

The group will unveil more tour and on-sale dates soon, according to the site.

Late last month, Van Halen [ tickets ] announced that Hagar--who replaced original singer David Lee Roth in 1985, then parted with the band on bad terms in 1996--had returned to the group. The reunited lineup plans to release a best-of set this summer that will also feature recently recorded material, including a cut titled "It's About Time."

A Warner Bros. spokesperson said additional details would be available later this week.

Van Halen's most-recent studio set is 1998's "Van Halen 3," which featured Hagar's short-lived replacement, former Extreme frontman Gary Cherone. Cherone left the group shortly after completing a tour in support of the album.

The group's most-recent album with Hagar is 1995's "Balance."