However, if one needs to improve on the design during the actual process of weapon production, one may have to go in for more tests, Dr MR Srinivasan, former chairman of the Atomic Energy Commission (AEC), said.

The view was echoed by former chief of air staff, air chief marshal NC Suri, who said that while data from this week's tests suffices for initiating a weapons programme, "additional tests would possibly be more prudent" for achieving higher levels of sophistication.

But a Russian military expert has estimated that India needs to conduct at least four more nuclear tests before it can go in for successful computer simulation and modelling.

According to Russian norms, to test one nuclear device four to five tests with it are necessary, the Russian business daily "Kommersant" reported quoting the expert.

Thesophistication of Indian computer modelling can help reduce this requirement to three tests per device, which means a total of nine tests, the Russian expert said.

Since five of these have already been conducted, four more are needed, he added. The need for more tests to collect data for further subcritical experiments was reiterated by Dr RR Subramanian, a nuclear physicist with the Institute for Defence Studies and Analyses (IDSA).

He said the data from the five field tests would be "limited" and probably not sufficient for use in computer simulation studies. "An enormous amount of field data is needed for such studies," he added. Suri said the five tests had undoubtedly given India the nuclear weapon capability as the country could now make various types of nuclear weapons suited for the country's specific needs and optimise their designs as well.

"From the scientific point of view, sufficient amount of data has been generated for computer simulation and this would no doubt help us in optimisingdesign as well as attaining the capability of carrying out subcritical experiments," he said.

According to PK Iyengar, former AEC chairman, the ability to test three very different kinds of nuclear devices, both fission and fusion, "unequivocally confers on India the status of a nuclear weapons state", irrespective of whether or not it chooses to maintain a stockpile of these weapons.

If one keeps in mind the original definition of a nuclear weapon state as one which has the ability to design and build nuclear weapons and conduct a nuclear test, then India can technically qualify as a nuclear weapon state after the Pokhran tests, Srinivasan said.

The number of tests a country has conducted is immaterial, he said.

But whether the international community will recognise India as one and how the five nuclear weapon powers will categorise the country is a different aspect, both Srinivasan and Subramanian pointed out.

The five recognised nuclear weapon powers - United States, Russia, Britain, France andChina - were those who produced N-weapons before 1967.

According to Iyengar, the tests will help India negotiate from a position of strength in international meetings.