MS Dhoni was an important illustration of the spirit of new India and a "phenomenon", prime minister Narendra Modi has said in a letter of appreciation to the cricketer.

Dhoni, who retired from international cricket on August 15, responded on Twitter by saying: "An Artist, Soldier and Sportsperson what they crave for is appreciation, that their hard work and sacrifice is getting noticed and appreciated by everyone."

"Where we come from does not matter as long as we know where we are headed," the prime minister said in his letter. "This is the spirit that you have exuded and inspired many youngsters with."

"Rising from humble beginnings in a small town, you burst onto the national scene, made a name for yourself and most importantly, made India proud," he wrote.

He said Dhoni's rise and conduct "gives strength and inspiration to crores of youngsters who like you haven't been to cushy schools or colleges, neither do they belong to illustrious families but they have the talent to distinguish themselves at the highest level.

"Many of your on-field moments exemplify a particular generation of Indians ... [that] does not hesitate to take risks and back each other's abilities even in the toughest situations ... [This was] seen in the way you took risks many a time in backing little-known youngsters to deliver in high-pressure situations," the letter said, referencing the 2007 World T20 final.

"This generation does not lose their nerve in decisive situations," the letter added.

Calling him one of the greatest captains and one of the best wicketkeepers the game has seen, the letter said: "Your dependability in tough situations and your style of finishing matches, particularly the 2011 World Cup final will forever be etched in the public memory for generations.

"The correct way to assess your impact is as phenomenon."