The accused vendor is yet to be arrested, they said.
Ashish Chowdhary, who is in his twenties, is posted as an assistant section officer in the ministry, whose office is located in Shastri Bhawan.
Around 12.15 PM, he had come out to buy a water bottle from a vendor opposite Krishi Bhawan, near his office, police said.
Chowdhary bought the bottle for Rs 20 but told the vendor that he had a Rs 500 note. To this, the vendor asked him to buy items worth Rs 50 as he "did not have enough change (money)".
More From This Section
Then Chowdhary told the vendor, "When you can return Rs 450 to me, you can also pay Rs 480."
The vendor lost his cool at Chowdhary's remark and took out a knife to attack him but was prevented by a CISF (Central Industrial Security Force) personnel posted there, police said.
Chowdhary, who suffered minor bruises, approached the police and a case was registered.
In the aftermath of the incident, the Ministry of Agriculture and Farmers Welfare has asked the New Delhi Municipal Council (NDMC) to act against "encroachers".
"The NDMC has been asked to take appropriate action against encroachers. Earlier, encroachers had left the place for almost two months after we had made a complaint to the Council. However, they have returned," said an official from the ministry.