Despite rising tensions with the West over its nuclear ambitions, many Tehran restaurants were fully booked and young Iranians could be seen out browsing gift shops in the capital to buy presents for loved ones in defiance of a ban on Valentine's Day items aimed at preventing the spread of "Western culture".

Iranian authorities banned the sale of Valentine cards and other heart-shaped products last year and police have warned that action will be taken against those who violate the ban.

"This year they told us not to sell any red roses otherwise we can face the closure of our flower shop," said a 40-year-old female florist in north Tehran.

Tension has been mounting between Iran and the West over the Islamic state's nuclear programme, which Washington and its allies say is a cover to build bombs. Iran denies this, saying it needs nuclear technology to generate electricity.

Foreign sanctions imposed on Iran over its refusal to halt the country's sensitive nuclear work, has had a negative impact on the country's economy.

Despite the hardship from sanctions and the state ban, many gift shops in Tehran are decorated with red ribbons, lights and candles to attract young customers, who mainly buy three red roses - one for each word in the English phrase "I love you".

Heart-shaped red balloons and soft toys are also a favourite, while rich Iranians opt for perfume and jewellery.

"I am certain, like previous years, we will run out of roses as lots of people have already ordered flowers for their loved ones," the florist said.

With Valentine's Day becoming increasingly popular over the past years, many Iranian youths are less afraid of being arrested for flouting the ban.

"Valentine's Day is finding its place in the hearts of many Iranian youths," said 21-year-old private sector employee Navazesh, who refused to give her surname.

"I feel different when I wake up on Valentine's Day."

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Valentine's Day has become a money-maker for businesses hard-hit by sanctions. Iran's economy is around 60 percent reliant on oil and the country is heavily dependent on food imports, buying 45 percent of its rice and most of its animal feed abroad.

Sanctions-linked trade snags risk fuelling already high inflation, which Iranian critics blame on Ahmadinejad's economic policies. The official inflation rate exceeds 20 percent.

Nonetheless, many restaurants in affluent northern Tehran -- who want to attract more customers -- have arranged dinners catered for lovers, and are offering a change of menu, live music and even fireworks, according to a waitress in an Asian restaurant.

Trying to get a reservation at fully booked restaurants to take his girlfriend for a "romantic" Valentine's Day dinner, 27-year-old university student Mehran said he is upset about limitations imposed by Iranian authorities on young people.

"Love knows no boundaries," he said, adding that despite his own financial hardship, he is willing to splash out on this particular day of the year.

Like many Iranian youths, Mehran said this was an opportunity to have fun in Islamic Iran.

Other Iranians see no reason for Valentine's Day celebrations, arguing that Iran is a civilised country with "various historical days to honour kindness and love."

"This is something encouraged by shop owners to earn more money," said government employee Mohammad Sarkari, 47.

Hardliners see Valentine's Day as part of a deliberate "soft war" waged by the West to corrupt Iran's youth.

But young Iranians with access to the internet are familiar with Western culture.

"I just want to live like other young people around the world. I feel like part of the global community when I celebrate Valentine's Day," said high school student Reza Khosravi.

Some nationalists have suggested replacing Valentine's Day with "Mehregan", an Iranian festival celebrated since the pre-Islamic era. Mehr means friendship, affection or love.

The Iranian opposition movement have called for a demonstration on February 14 to mark the year-long house arrest of opposition leaders, Mirhossein Mousavi and Mehdi Karoubi.

Authorities said on Sunday they will crack down on any protest by the opposition, which says Iran's 2009 presidential vote was rigged to secure Mahmoud Ahmadinejad's re-election.

The eight months of protests which followed the vote were suppressed by Iran's security forces.

"I don't care about demonstrations. I want to have fun. I want to love and to be loved," said Khosravi, while buying three red roses for his girlfriend in a central Tehran flower shop.

(Editing by Paul Casciato)

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