In the port city of Karachi, home to 18 million people, billboards decorated with a black heart urged citizens to "SAY NO TO VALENTINE'S DAY."
"This tradition reflects insensitivity, indignity and ignorance of Islam," the signs read. They were put up by a group affiliated with Jamaat-e-Islami, a religious political party that holds six of 342 legislative seats.
Secular parties dominate Pakistani politics and are likely to win the vast majority of votes in elections due this year, but religious parties often wield political influence through street demonstrations.
"Valentine's is against Islamic culture. In our view, relationships are sacred. We have arranged marriages in this culture and people don't get married for love," said Syed Askari, a spokesman for Jamaat-e-Islami. "This is imposing Western values and cultures on an Islamic society.
"Look at the West - people love their dogs but throw their parents out when they get old. We don't want to be like that."
In the northwestern city of Peshawar, a handful of people burned Valentine's Day cards in front of television cameras on Monday. Women wearing black robes held signs denouncing the tradition.
The state broadcasting regulator, PEMRA, urged broadcasters to "respect viewers' sentiments."
"PEMRA has been receiving complaints from a large segment of society that Valentine's Day celebrations are not in conformity with our religious and cultural ethos and has, therefore, condemned its unequivocal propagation through media," the statement said.
But in the capital of Islamabad, hawkers selling heart-shaped balloons staked out street corners and florists were doing a brisk trade.
"Valentine's Day is good for business," said a grinning Mohammed Ajmar as he handed a customer a huge heart made of red roses and glitter.
"I'm happy with Valentine's Day. The city if full of flowers and it looks nice," said 21-year-old student Faateh Khan, who was buying roses for his mother. "Those people are just a minority of extremists acting up for the media," he said of those making complaints.