Indian and Pakistani hackers are engaged in a round of tit-for-tat defacing of government-run websites of the two countries, targeting such major organisations as India's oil and gas major ONGC and its Pakistani counterpart OGRA.

The cyber warfare began in mid-November when an Indian group of hackers known as HMG or "Guards of Hindustan" defaced the website of Pakistan's Oil and Gas Regulatory Authority and deleted all its data.

The move created a buzz in cyberspace as HMG had earlier hacked a number of Pakistani communities on the social networking website Orkut.

Apparently acting in retaliation, a group calling itself the Pakistan Cyber Army (PCA) on Tuesday hacked five Indian websites, including those of ONGC, Indian Institute of Remote Sensing (IIRS), Indian Railways and the Kendriya Vidyalaya in Ratlam.

While the websites of ONGC and Indian Railways were quickly restored, the IIRS website is still blank. In a message posted briefly on the ONGC website, PCA said the hacking was carried out in retaliation for the hacking of the OGRA website.

"Back off, go read some course books, else you will lose both, your name and this game. We will literally smoke your doors off like other groups did before," said the message from PCA.

Responding quickly to the actions of the PCA, HMG took control of the website of Kendriya Vidyalaya in Ratlam. The website still features a message from HMG asking the site owner to fix its "flaws."

"Ur site was hacked by Pakistani hackers, now ur site is in our Indian hackers' control," said the message from HMG.

After internet usage became popular in the Indian subcontinent in the early 1990s, Indian and Pakistani hackers including those based in the West often engaged in tit-for-tat defacing of websites of both countries.

Those activities subsided after a few years. Hackers cannot control a website permanently even if they break into it.

They usually post a fake page on a hacked website.

Ironically, PCA has asked Indian authorities to take action against HMG for hacking Pakistani websites "or get ready for more action."