Sri Lankan spinner Ajantha Mendis has been ruled out of the Test series against Bangladesh due to an ankle injury.

Mendis, Sri Lanka's top bowler this year, had injured his ankle during the one-day series in Zimbabwe and dropped from the Test team.

Sri Lankan selectors have picked left-arm spinner Rangana Herath to replace Mendis in the squad.

Mendis, however, is expected to be fit in time for the triangular one-day tournament which follows the two Tests.

Zimbabwe are the third team participating in the competition which is scheduled to start from January 10.

"The injury will take at least three to four weeks to heal," Sri Lanka team physio Ranjith Nanayakkarawasam said.

Herath, who last played a Test against the West Indies in March this year, made his Test debut against Australia in 1999.

He has claimed 35 wickets from 13 Test matches at an average of 37.22.

The first Test between Sri Lanka and Bangladesh is due to begin in December 26 in Dhaka.