Speaking during a military pageant to commemorate the 2009's victory over Tamil Tiger rebels, Rajapaksa said that the critics were trying to bring the country's armed forces into disrepute.
"The military victory over the Tamil Tiger rebels in May 2009 was a result of a decades-long war," The BBC quoted Rajapaksa, as saying.
The President added that the operation was carried out only to eliminate terrorism.
"Our armed forces comprise those who went into battle carrying a gun in one hand, the declaration of human rights the other, as well as taking food for the liberated people of the north and full of human kindness in their hearts," Rajapaksa said.
He expressed his concern that Tamil people in the north have been deprived of development of roads, electricity and schools and promised to improve their conditions by the end of this year.
All of the country's top leaders attended the ceremony, except, General Sarath Fonseka, the man who commanded the army during its struggle against the Tamil rebels.
Fonseka is currently in detention, but the government clarified that his absence was because of security reasons.