Nick Childs BBC foreign affairs correspondent

India has now tested an intermediate-range version of its Agni missile, capable of carrying out a nuclear warhead, however it insists that the test was carried out for technical, not political reasons, and had been long planned.

That may well be true, however there can be little doubt that Delhi would have been aware of the political impact of the test at this time.

The missiles are easily capable of hitting Pakistan

In a sense, going ahead with the test was probably meant by the government to send a message to its domestic audience, to Pakistan, and to the wider international community that India is determined to assert its security interests.

And it can be seen very much in the context of India's so-called "coercive diplomacy", as many have described it, on Pakistan to do more to crack down on "cross-border terrorism", as India describes it.

The version of the Agni missile tested was an intermediate one; according to Indian officials, the test was over a range of less than 700 kilometres (440 miles) - easily capable of hitting Pakistan.

Some estimates put the maximum range of this Agni 1 missile at about 1,000 km, putting China within range.

But clearly its military value, and rationale, is more in the context of the balance of power with Pakistan, rather than with a country such as China.

Triangular relationship

Still it is this triangular strategic relationship which so exercises the international community.

India's and Pakistan's recent military mobilisations have raised questions in the minds of some analysts about the deterrent value of nuclear weapons in this region

India, Pakistan, and China are all nuclear powers, and certainly in the development of its nuclear deterrent doctrine, Delhi is as conscious of Beijing as it is of Islamabad.

That is one reason why India has also been developing a much longer-range Agni 2, capable of hitting targets 2,500 km away, and even an Agni 3, with a reach of 3,500 km.

Delhi carried out a test of the Agni 2 almost exactly a year ago, and there is also the much shorter-range Prithvi system.

This development programme has been under way for well over a decade.

India insists that it is pursuing a no-first-use and minimum deterrent nuclear policy, and in that context the different systems cover the main threats it feels it is likely to face.

Deterrent value?

However, India's and Pakistan's recent military mobilisations, and their apparent willingness to contemplate a limited conventional confrontation, have raised questions in the minds of some analysts about the deterrent value of nuclear weapons in this region.

India and Pakistan traded tit-for-tat missile tests in 1998

Conversely, others say the fact that these tensions have not boiled over already, given the level of emotion on both sides, is both a credit to the two governments, and a reflection of the very presence and deterrent value of their nuclear arsenals.

Still, there is little doubting the topic's sensitivity, nor is this the first time such tests have brought tensions to a head in the region.

India and Pakistan carried out tit-for-tat nuclear tests in 1998, which set alarm bells ringing around the world.

And some analysts believe that India was encouraged to go ahead with its test detonation in part at least by a Pakistani test of long-range missile just five weeks earlier.