MS Dhoni has credited Zaheer Khan and the other bowlers for the thumping ten-wicket victory over Bangladesh that secured a clean sweep.

Bangladesh had frustrated India by moving along to 290 for 3 soon after the drinks break in the morning session, and were even looking good to pose a stiff challenge for the injury-riddled Indian batting line-up in the fourth innings.

However, they imploded spectacularly - losing their final seven wickets for 22 runs - to be bowled out for 312, and setting India a target of just two runs. The collapse was sparked by the spinners before the pace and movement of Zaheer wrapped up the innings three deliveries after lunch.

"It was a difficult task to get wickets in this track, both for spinners and pacers," Dhoni said after collecting the series trophy. "But all credit goes to the bowlers. They really put their best to get those 20 wickets, especially Zaheer's spell.

"The ball was getting old and the wicket was getting slower and slower," he said. "This is a reason we decided to bowl first in this wicket. If you bat first you need to score 600 plus or else you have to again come and bat. So it was tough but I think the bowlers did a terrific job."

Zaheer picked up a career-best 7 for 87 in the second innings, and his first ten-wicket haul to be named Man of the Match, and also bagged the Man-of-the-Series award. He was out of action for several months last year after a major shoulder operation in July, and only returned during the home series against Sri Lanka two months ago.

He said the incisive spell with the old ball has boosted his confidence but warned that he was still short of his best. "I am happy the way my spell went today and it has boosted my morale," he said. "I still need to work on my fitness. My shoulder needs to be monitored and I have to do the rehab exercises."

The win also improves Dhoni's captaincy record to eight wins in 11, and completed India's fifth consecutive series victory, increasing their lead at the top of the Test rankings by a point. "We always can do better. For the last 12 months we have done well in both ODIs and Tests," he said. "There is always scope for improvement but the result is very satisfactory."

The one source of concern for Dhoni is injuries to three of his middle-order batsmen - VVS Laxman, Rahul Dravid and Yuvraj Singh. Laxman missed the second Test in Mirpur with stitches to his hand, Dravid has a jaw fracture and Yuvraj has a torn ligament in his left wrist and there's still a question mark over their availability for the series against South Africa next month. "The series was full of injuries so I am a bit worried. But with the amount of cricket that we play these days, it is okay. I hope the players (VVS Laxman and Yuvraj Singh) are fit before the South Africa series."