"Satyender Jain starts indefinite fast," Kejriwal tweeted from the office of lieutenant governor Anil Baijal.
Jain began his fast from the L-G's office at 11 am.
Kejriwal, his deputy Manish Sisodia, Development Minister Gopal Rai and Jain met Baijal at 5.30 pm yesterday and have since stayed on.
There is heavy police deployment as AAP leaders and workers have been trying to reach the L-G's office since last night.
With police barricading the area, AAP leaders, MLAs and workers have been staging a sit-in outside the chief minister's residence, about two kilometres from the L-G Secretariat.
Sisodia said on Twitter that that the chief minister and his three ministers have been sitting in the 'waiting room' of the L-G's office for 18 hours. But the L-G was adamant on his decision that he will neither get the officers' strike called off nor get the file of doorstep delivery of ration cleared, he said.
The L-G's office slammed Kejriwal's sit-in, saying it was one more "dharna without reason".
A statement, issued by Baijal's office last evening, stated that the L-G was "threatened".
In the morning, a letter, signed by Kejriwal, Sisodia, Rai and Jain, was sent to Baijal. It asked him to take all necessary steps to end the "strike" by IAS officers, including issuing written orders that proceedings would be initiated against all officers who do not return and "if necessary, ESMA may be invoked".
According to the government, IAS officers have been on strike since the alleged assault on Chief Secretary Anshu Prakash and are boycotting meetings with AAP ministers, affecting public work.
However, the officers association has claimed that nobody is on strike and no work has been affected.
"Handed him this letter. LG refuses to take action. LG is under constitutional duty to act. Left wid no option, we have politely told LG that we will not leave till he acts on all points.
"We hv come out of his chamber n sitting in his waiting room (sic)," Kejriwal tweeted last evening after he along with his three ministers started their sit-in.
The AAP government and the bureaucracy have been at loggerheads since the alleged assault on Prakash by AAP MLAs at Kejriwal's residence on the intervening night of February 19-20.