Wagner, 37, who has taken 258 wickets in 67 Tests for the Kiwis at an average of 27.50, has had previous stints with Essex, Lancashire and Northamptonshire.

He replaces fellow Kiwi Matt Henry, who is part of the white-ball squad that faces England in four ODIs and four T20s.

Henry, 31, took 32 wickets in six Championship games and was a key part of the Somerset team that won the T20 Blast last month.

Wagner will not feature in any of the One-Day Cup fixtures this month, but will be eligible to make his debut against Hampshire on 3 September when the Championship resumes.

"We have been working extremely hard to secure the services of a quality international bowler for the last three red-ball fixtures of the season," director of cricket Andy Hurry told the club's website.

"Neil is a proven performer at the very highest level and has vast experience as well as a thorough understanding of Championship cricket."