Mastodon have cancelled 16 tour dates.

The heavy metal band were scheduled to play a string of international shows including the prestigious Reading/Leeds Festival throughout August and September but have pulled out of all of the gigs citing a ''personal family matter''.

The group - featuring Troy Sanders, Brent Hinds, Bill Kelliher and Brann Dailor - have not issued a personal statement expanding on what has prompted them to axe the planned dates, which included appearances at Pukkelpop in Belgium, Oya Festival in Norway and Heavy Montreal Festival, where they were due to perform on August 7.

The band were due to headline The Pit at Reading and Leeds Festival but have now been replaced by Swedish metal band Ghost, while their show in Iceland on September 5 will now take place at Reykjavik's Rokkjotnar Festival on December 5.

The outfit released their sixth studio album Once More 'Round the Sun' last year reaching their highest chart positions to date, with guitarist Brent recently joking they chose a lighter sound for the record compared to 2011's 'The Hunter' because he ''never really liked heavy metal in the first place.''

Mastodon are expected to return to the stage at the Rock in Rio festival in Rio de Janeiro, Brazil, on September 25.