Twitter said Wednesday it had blocked some accounts in India over comments on mass farmers' protests in New Delhi, but the social media giant refused to shut down others despite the threat of criminal action by the government.

Indian officials last week demanded that Twitter block hundreds of users that have tweeted on demonstrations against proposed new agriculture laws, saying they were a "grave threat to public order".

Twitter initially complied by blocking a number of accounts -- including those of a prominent news magazine and farmer groups -- but unblocked them several hours later, prompting threats of "penal action" from the government. 

Farmers have camped on roads leading into the capital since late November as they call for the new laws to be repealed, in one of the biggest challenges to Prime Minister Narendra Modi's government since it came to power in 2014.

International celebrities including pop superstar Rihanna and climate activist Greta Thunberg have even weighed in on the protests online, drawing the ire of the foreign ministry, which called their comments "sensationalist". 

In a blog post, Twitter said it did "not believe that the actions we have been directed to take are consistent with Indian law".

"In keeping with our principles of defending protected speech and freedom of expression, we have not taken any action on accounts that consist of news media entities, journalists, activists, and politicians," the San Francisco-headquartered company said. 

"To do so, we believe, would violate their fundamental right to free expression under Indian law."

But the firm nevertheless said several accounts had already been "permanently suspended", while some others had been blocked but only "within India".  

Twitter's response comes as a tussle intensifies between India's authorities and social media services.

Local media reported that New Delhi has accused Twitter of bias, saying its chief executive, Jack Dorsey, had liked tweets by celebrities supporting the farmer protests.

Some local personalities including Commerce and Industry Minister Piyush Goyal have opened accounts on rival Indian social network platform Koo.

Prime Minister Modi remains an active Twitter user with 65.5 million followers, the most of any world leader.