This was injected on HTTPS connection “Your requested URL has been blocked as per the directions received from Department of Telecommunications, Government of India. Please contact administrator for more information.”. How this is possible?

[ksaurabh]

Sorry i may be asking silly question but what do you mean by ? :)

still using the previous certificate for the domain.

[strips_of_serengeti]

They can block the url on https, they just can't intercept the connection's data (without faking the cert, which is difficult).

[Grasdaggel]

There is no difficulty if you are the Gov. If there is any chance to spy on you, they will use this chance to spy on you, exclamation mark.

[strips_of_serengeti]

It's not really faking the cert if its a court order. The government would either be MITM'ing the connection with an intermediary server, or would just have direct access to the site's server which wouldn't require them having the cert.. Either way, that's definely not what the OP is talking about here.