Out of the 140 new cases, 122 are from Guwahati city, which is under complete lockdown for 14 days since June 28.
The state now has 2,885 active cases. While 5,647 patients have recovered and discharged from hospitals, 12 died and three migrated to other states.
Assam registered the highest single-day spike of 613 cases on Tuesday and 382 of them were from Guwahati. Since June 24, 1,362 people have tested positive for COVID-19 in the city.
The state government imposed a 14-day complete lockdown in Kamrup (Metro) district, of which Guwahati is a part, from June 28. The move followed the detection of 762 positive cases in the city in a week since June 15.
Of them, 677 people do not have travel history though many had come in contact with returnees.
Sarma said Union Home Minister Amit Shah called him up after the Indian Council of Medical Research (ICMR) expressed apprehension that Guwahati is assuming an "alarming situation on the lines of Mumbai and Delhi".
Shah held a meeting with the ICMR director general and the health and family welfare secretary on the Guwahati situation in New Delhi on Tuesday, he said.
The Union minister also asked Sarma to open more testing facilities and advised people to maintain the lockdown restrictions strictly.
Meanwhile, Sarma inaugurated the 13th testing laboratory of the state at the Mahendra Mohan Choudhury Hospital in Guwahati.
"We have been continuously increasing our testing ability and improving our medical infrastructure," he said.
The state is the third in the country after Tamil Nadu and Andhra Pradesh as far as testing is concerned with 4,12,214 samples tested so far, he said. DG NN KJ KJ KJ