Accusing the central government of "deploying the army" along a highway toll plaza, which is at the second Hooghly Bridge and about 500 m from the secretariat, Banerjee had previously said that the state government was kept "in the dark".
"I won't leave unless the army is withdrawn from near the secretariat. I'll keep vigil to protect democracy, to protect my democratically elected government," Banerjee told a hurriedly convened late night media meet on Thursday at the secretariat Nabanna in neighbouring Howrah district.
A little after midnight, the Eastern Command said the army has been asked to withdraw from the toll plaza near Nabanna as it had already collected the data it required.
Past 2 a.m., Banerjee -- holding her third round of media conference since the evening -- reiterated she would spend the night at Nabanna, fearing the Army may be back.
"The army has withdrawn from the second Hooghly Bridge after 2 am. They will definitely come back. After Nabanna, they have entered various districts. The army has been deployed in 80 per cent of the areas," she said.
"I'll remain awake all night to keep vigil. I will spend the night at Nabanna," she said.
The riveting drama unfolded on Thursday evening, when Banerjee alleged the army has been deployed at the Dankuni and Palsit toll plazas on National Highway 2 (connecting Delhi and Kolkata) without informing the state government.
She said the Chief Secretary was writing to the central government and she would approach President Pranab Mukherjee seeking clarification on the issue.
"This is unacceptable. Federal structure has been disrupted and democracy twisted. Has Emergency been declared?" she asserted.
The Defence Ministry said the army was conducting routine exercise with full knowledge of and co-ordination with West Bengal police.
"The army conducts the annual exercise throughout the country with the aim of getting statistical data about the load carriers that could be made available to the army in case of a contingency," said a Defence ministry spokesman.
Around 10 p.m., Banerjee held the second round of media conference, rubbishing the spokesman's clarification and declaring she would camp at the secretariat.
"The National Highway Authority of India has all this data. They have records of the number of cars plying in each state, and through each highway."
She also tweeted: "Absolutely wrong and misleading facts byA@easterncomdAWe have great respect for you, but please please don't mislead the people."
Banerjee, also supremo of the ruling Trinamool Congress, said she has collected information from Maharashtra, Kerala, Odisha and Chhattisgarh and nowhere such a thing was been done.
"Why is it been done in Bengal? Is it because I am speaking for the people?" she asked, claiming the army has been positioned in Jalpaiguri, Alipurduar, Darjeeling, North 24Parganas, Howrah, Hooghly, Kolkata, Murshidabad and Burdwan districts.
Banerjee said: "The secretariat "Nabanna" is a sensitive zone. The toll plaza on the second Hooghly Bridge is within the sensitive zone. It is under our secretariat."
Demanding to know whether a military coup has taken place, she said "the motive is political, vindictive, unconstitutional, unethical and undemocratic".
Besides the Chief Minister, a number of ministers and the Home Secretary, State Director General of Police, the Kolkata Police Commissioner were all camping at the secretariat.
Banerjee said despite the city police commissioner informing the army about the state government's objection to their presence, the army men had refused to budge.
Banerjee alleged that the army was taking money from the people at the toll plazas, and called it "loot".
"Even if the Army carried out a mock exercise, the state government should have been kept in the loop. If this is happening in a civil area in Bengal, this could happen in Bihar, next in Uttar Pradesh, then in Tamil Nadu and other states as well. It is a very serious situation and it is dangerous than Emergency. We are facing an extremely black day," she said.
"I'll urge all state governments to look into the matter. A team of Opposition... all political leaders... will meet the president (soon)," she added.
Soon after Banerjee's allegations, the spokesman said the routine exercise was being carried out in all states of the eastern region.
"Permission for carrying out this exercise in West Bengal was initially sought for November 28. On specific request of the police the date had been shifted to December 1. No permission has been withdrawn so far," the spokesman added.
"Routine exercise in all NE states. In Assam @ 18 places, Arunanchal@13, WB@19, Manipur@6, Nagaland@5, Meghalaya@5, Tripura & Mizoram," the Eastern Command tweeted.
But the Kolkata police said they had given their objection in writing.
"Army exercise at Toll Plaza was objected to in writing by Kolkata Police, citing security reasons & traffic inconvenience," the Kolkata police claimed on its twitter handle.