Addressing tens of thousands after taking oath at the vast Ramlila Maidan, Kejriwal said this was a "historic day" but the path ahead would be long and challenging.
"Today is a historic day," the 45-year-old said in opening remarks, triggering wild cheering from the sea of supporters packing the ground in the heart of Delhi.
"Today every citizen in Delhi has taken the oath of office."
For a long time, the activist-turned-politician said, people across the country had become despondent that nothing good could happen in this country.
"People felt that bad politics had destroyed everything.
"But the people of Delhi proved that even honest people can fight and win elections."
He said the AAP's decision to form a government in Delhi "is only the beginning. The real fight lies ahead.
"Kejriwal or his ministers cannot fight this battle all alone... But I am convinced that if the people of Delhi get together, then we can eradicate corruption."
In the face of rising expectations from his government, Kejriwal advised patience and said he had no "magic wand" to solve all their problems.
"We do not believe we have all the answers to all the problems, or that God has given wisdom only to us.
"But if we all get together, then there is no problem that cannot be resolved."
He made it clear that the AAP government would not be run by politicians, officials and police but by ordinary people. "This is your government."
Kejriwal recalled that Gandhian activist Anna Hazare, who he regards as his guru, used to say that politics was dirty.
"I used to tell him that if it were so, then we will have to plunge into this muck to clean it up."
Ascribing all the ills of the nation to "dirty politics", Kejriwal said his meetings in the past few days with officials in Delhi made it clear that most of them were honest.
"Delhi's bureaucracy will have to join hands with the people ... so that we can rid this country of corruption and banish poverty."
He warned that those upset by the AAP's victory "won't keep quiet.
"They will create many obstacles... I am getting a lot of information. It is not correct for me to make these public now.
"I am convinced they are going to create roadblocks."
The AAP founder leader said he was not worried whether or not he is able to prove his majority in the 70-member assembly Jan 3.
He said that if the AAP failed to prove its majority, "we will return to the people... People are ready for (fresh) elections.
"And in the next election, the AAP will be returned to power with a thumping majority."
--IANS (Posted on 28-12-2013)