Geneva, Switzerland — Nuclear-armed countries hiked spending on atomic weapons arsenals by a third in the past five years as they modernized their stockpiles amid growing geopolitical tensions, two reports showed on Monday.

The world’s nine nuclear-armed states jointly spent $91 billion on their arsenals last year, according to a new report from the International Campaign to Abolish Nuclear Weapons (ICAN).

That report, and a separate one from the Stockholm International Peace Research Institute (SIPRI), indicated that nuclear weapons states are dramatically scaling up spending as they modernize and even deploy new nuclear-armed weapons.

“I think it is fair to say there is a nuclear arms race under way,” ICAN chief Melissa Parke told AFP.

Wilfred Wan, head of SIPRI’s weapons of mass destruction program, meanwhile, warned in a statement that “we have not seen nuclear weapons playing such a prominent role in international relations since the Cold War.”

SIPRI’s report showed that the total estimated number of nuclear warheads in the world actually declined somewhat to 12,121 at the start of this year, from 12,512 a year earlier.

But while some of that included older warheads scheduled to be dismantled, it said 9,585 were in stockpiles for potential use — nine more than a year earlier.

And 2,100 were kept in a state of “high operational alert” on ballistic missiles.

Nearly all of those were held by the United States and Russia, but China was for the first time believed to also have some warheads on high operational alert, SIPRI said.