It may have given the world the Kama Sutra and the Bollywood wet sari scene, but it appears that India is not yet ready to be exposed to the delicate subject of sex on the internet.

A Guardian investigation has discovered that several internet companies have quietly introduced filters to prevent Indian users from accessing sexual content.

The Yahoo search engine and Flickr photo-sharing site (owned by Yahoo) altered their sites earlier this month to prevent users in India from switching off the safe-search facility. The block also applies to users in Singapore, Hong Kong and Korea.

Microsoft has also barred Indian users of its Bing search engine from searching for sexual content. Users who do try to search for sexual material receive a notice informing them that "your country or region requires a strict Bing SafeSearch setting, which filters out results that might return adult content".

The clampdown is understood to be in response to recent changes to India's Information Technology Act of 2000, which bans the publication of pornographic material.

That law, which is based on a 150-year-old statute (section 292 of the Indian penal code), defines obscenity as "any content that is lascivious and that will appeal to prurient interest or the effect of which is to tend to deprave or corrupt the minds of those who are likely to see, read or hear the same".

In October, the scope of the 2000 act was dramatically widened to enable action to be taken against a wide range of providers, from internet search engines and internet service providers to cyber-cafes. Under the new law, they are obliged to exercise due diligence and disable access to any content which contravenes the act. Failure to do so carries a three-year jail sentence and a fine of up to 500,000 rupees (£6,690).

Search engine reports suggest that users in India are responsible for more searches for "sex" than those in any other country. Its popular daily newspapers are packed with pictures of young women in states of undress and Bollywood oozes sexuality from every pore.

But at the same time it remains a deeply religious country in which traditionalists regularly take violent offence at anything deemed to be too suggestive.

The latest attempts to constrain internet users come at a time when the vexed subject of sexual behaviour is once again dominating the domestic headlines.

Last week an Indian news channel broadcast video footage of a man said to be the 86-year-old governor of Andhra Pradesh, Narayan Datt Tiwari, in bed with three young women. He quit on Sunday, citing health reasons and still denying that the man in the video was him.

Today there was also mixed news for the tens of thousands of fans of India's most popular – and only – cartoon porn star, Savita Bhabhi.

The sexual antics of the energetic housewife won her website a daily audience of nearly 200,000 visitors, until it was closed down by the Indian government in June.

Now the site is back at a new web address but already it has fallen foul of the Internet Service Providers Association of India, whose president, Rajesh Chharia, warned that it faced closure again because its content was "not acceptable to our culture".

No one from Yahoo was available for comment today but a posting on the Flickr website explained that "Flickr is a global community made up of many different kinds of people.

"What's OK in your backyard may not be OK in theirs. Each one of us bears the responsibility of categorising our own content within this landscape. So, we've introduced some filters to help everyone try to get along.

"If your Yahoo! ID is based in Singapore, Hong Kong, India or Korea you will only be able to view safe content based on your local terms of service (this means you won't be able to turn SafeSearch off)."