Copenhagen, June 17 : Nuclear weapons states are strengthening their nuclear arsenals in the face of numerous conflicts worldwide, a leading Swedish think tank on conflict and defence said on Monday.

According to a new report published by the Stockholm International Peace Research Institute (SIPRI), the number of operational nuclear warheads is steadily rising.

"While the global total of nuclear warheads continues to fall as Cold War-era weapons are gradually dismantled, regrettably we continue to see year-on-year increases in the number of operational nuclear warheads," said SIPRI director Dan Smith.

"This trend seems likely to continue and probably accelerate in the coming years and is extremely concerning."

The number of nuclear weapons in development is also on the rise, as states bank on nuclear deterrence, the report said.

Of the estimated total of 12,121 warheads recorded worldwide in January, around 9,585 were part of military stockpiles for potential use.

Around 3,904 of these warheads were mounted on missiles and aircraft - 60 more than in the same month a year earlier. According to the report, the rest were kept in centralized storage facilities.

For decades, the global number of nuclear weapons has been steadily declining. However, the decline is mainly due to the fact that discarded warheads are gradually being dismantled by Russia and the US following the Cold War.