New Delhi  - Indian police detained up to 600 right-wing Hindu activists on Saturday, following sporadic protests and harassment against young couples celebrating Valentine's Day, news reports said.

Members of the hardline Shiv-Sena group, blackened the faces of couples at a park at the Moradabad city in northern Uttar Pradesh, the NDTV network reported.

They also attacked three couples and cut their hair at India's famous monument to love, the Taj Mahal in the state's Agra city.

The fundamentalist group said it was holding protests across the country against Valentine's Day celebrations which it said were against Indian culture and had a "corrupting influence" on Indian youth.

Valentine's Day has become popular in India over the past decade with shops selling romantic cards, heart-shaped balloons, cuddly toys and other gifts, while flower sellers are doing brisk business.

But the day has also seen regular protests by Hindu and Muslim hardliners who claim the celebrations threaten Indian culture and social norms.

In the central Ujjain city, Bajrang Dal, another hardline Hindu group targeted siblings mistaking them for couples.

A "brother and sister were chased by activists on bikes. The boy was thrashed before being rescued by the police," police official Manmeet Narang told reporters.

In New Delhi, Mumbai and Bangalore police kept tight vigil at parks, malls and pubs to thwart protests.

But celebrations were muted as the couples kept a low profile - reflected in the slack sales at gift and flower shops, restaurants and malls.

In southern Bangalore and Mangalore cities, nearly 500 party workers, including the leader of the Sri Ram Sene party were taken into preventive custody in a police crackdown since Friday evening.

Police also tightened security and detained over 100 Shiv Sena and Bajrang Dal members across cities including national capital Delhi and Mumbai.

"We will not tolerate any protests or violence. Shops selling Valentine cards, pubs and restaurants were given protection and no untoward incident has been reported," Bangalore police chief Shankar Bidri said.

The Sene's attack on young women in a pub in Mangalore last month had triggered national condemnation that the "Hindu moral police" was forcing traditional mores on the society.

The Sri Ram Sene, dubbed as Indian Taliban by media channels, withdrew its threat to forcibly marry off the couples in face of a public outcry.

To protest Sene's threats, thousands of youth formed groups on social networking sites such as Facebook to launch a campaign to send pink knickers to the Sri Ram Sene and its men. Another group called on the people to throng the pubs and defy the group.

"It is the right of every human being to express love. No religion bars this so who are these self-appointed moral brigades to tell us what to do?," Sarika Mirajkar, bank employee in Mangalore said.

Activists of a radical Islamic women's group Dukhtaran-e-Millat also held protests in India-administered Kashmir and tore up Valentine's Day's cards in a gift shop in state capital Srinagar.

Some protests by Hindu groups were also reported from the eastern state of Orissa. They carried saffron flags and chanted slogans such as "Save Culture" and "Death to Valentine's Day." (dpa)