An extremist Hindu organisation has threatened to forcibly marry couples who publicly display affection on Valentine's Day in western Uttar Pradesh state.

Leaders of the Hindu Mahasabha warned that couples seen holding hands, hugging and holding flowers on 14 February will have to marry as a consequence for celebrating the "foreign festival", The Times of India reported.

"We are not against love, but if a couple is in love then they must get married. In case if the couples claim that they need time to think about marriage, we will tell them that if they are not certain, they should belittle love by openly going around together. We will also inform their parents," Mahasabha national president Chandra Prakash Kaushik said.

"India is a country where all 365 days are days for love. Why then must couples observe only February 14 as Valentine's Day?"

It is also believed that the group intends to monitor social media to force couples who declare their love online to marry.

The organisation's announcement was met with outrage and dozens of people publicly criticised the group on Twitter.

Hindu Mahasabha previously said that it would hold a Prem Vivah Diwas or Love Marriage Day on 14 February to encourage Hindu and inter-faith couples to get married.

Non-Hindu couples will have to convert to Hinduism through a process called Ghar Wapsi.

"The Ghar Wapsi of the Muslim/Christian partner will be done an hour before the wedding. For that we are asking couples to inform us a day before so we can make arrangements," Kaushik told Economic Times at the beginning of February.

This is not the first time that leaders of Hindu Mahasabha have sparked outrage in India. At the end of January, the group was criticised for saying it intended to install statues of Nathuram Godse, the man who killed Mahatma Gandhi, in temples across the country.