Indian celebrities on Wednesday hit back at pop superstar Rihanna and climate activist Greta Thunberg for making social media comments about mass farmers' protests.

As the government and farmers set out ever tougher positions in their two month-old battle over new agriculture laws, sporting legend Sachin Tendulkar and a host of Bollywood stars hit out at what the foreign ministry called "sensationalist" Twitter comments.

Rihanna, who has more than 100 million Twitter followers, wrote "why aren't we talking about this?!", with a link to a news story about an internet blackout at the protest camps where tens of thousands of farmers have been since November.

Superstar Rihanna has infuriated the Indian government by tweeting in support of protesting farmers
Superstar Rihanna has infuriated the Indian government by tweeting in support of protesting farmers AFP / Martin BUREAU

More than one million people retweeted, liked or commented on her Tweet.

Swedish climate activist Greta Thunberg also tweeted a story about the blackout, saying: "We stand in solidarity with the #FarmersProtest in India." Meena Harris, a niece of US Vice President Kamala Harris -- whose mother was born in India -- added her support.

The celebrity tweets triggered an online storm in India, where the protests have become the biggest challenge to Hindu nationalist Prime Minister Narendra Modi since he took power in 2014.

Swedish climate activist Greta Thunberg has also tweeted in support of the protesting Indian farmers
Swedish climate activist Greta Thunberg has also tweeted in support of the protesting Indian farmers AFP / Jonathan NACKSTRAND

"The temptation of sensationalist social media hashtags and comments, especially when resorted to by celebrities and others, is neither accurate nor responsible," said the foreign ministry.

Tendulkar, cricket's highest scoring international, led the Twitter riposte by Indian celebrities.

Thousands of Indian farmers have been protesting against a new law they fear will allow big corporations to take over the sector
Thousands of Indian farmers have been protesting against a new law they fear will allow big corporations to take over the sector AFP / Sajjad HUSSAIN

"India's sovereignty cannot be compromised. External forces can be spectators but not participants," he said.

Bollywood actress Kangana Ranaut, a Modi supporter, called the protesting farmers "terrorists" and Rihanna a "fool".

Actors and directors Anupam Kher, Akshay Kumar, Suniel Shetty and Karan Johar joined the fray against the "foreigners".

The government later threatened Twitter with "penal action" for unlocking 250 accounts and tweets on the farmers' protests that the US company had earlier blocked. Twitter took the initial action following a government notice, but reversed course after a few hours.

Among accounts targeted was a prominent news magazine and others linked to farmer unions.

The Electronics and IT ministry said Twitter had "unilaterally" unblocked the accounts and content and that it was "obliged" to obey government orders. "Refusal to do so will invite penal action."

A senior ministry official told AFP that the blocking order had targeted content that had the hashtag "#ModiPlanningFarmerGenocide" and not general comments about the protests.

India has also faced criticism from media watchdogs over the arrest of a journalist covering the protests and investigations launched into five others -- who could face sedition charges.

Amidst the war of words, authorities stepped up pressure on the protest camps, putting up barbed wire fences around some and laying down spikes on roads leading to them so that tractors cannot bring more reinforcements.

But at a rally attended by an estimated 50,000 people in Haryana state, farmers leader Rakesh Tikait vowed to mobilise thousands more farmers for the Delhi protests where a day of action is planned for Saturday.

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