The problem is whether we can treat assurances that there are no nuclear weapons in Kaliningrad as credible

Polish Defence Minister

Russian officials have flatly denied the report.

Poland, which joined Nato last year, said the use of international inspectors would end the speculation.

"We hope Russia would give its agreement to such inspections," government spokesman Krzysztof Luft told Polish radio.

"Poland would like this solution," he added.

Polish Defence Minister Bronislaw Komorowski said the government was taking the issue very seriously, and its "appropriate services" were analysing the reports.

A Pentagon official called the missile movements are "disturbing"

"The problem is whether we can treat assurances that there are no nuclear weapons in Kaliningrad as credible," said Mr Komorowski.

The Baltic states are also monitoring the situation closely.

"If it (the deployment) is true, it is very sad and we would have to make a statement," said Estonian defence spokesman Madis Mikko.

Concern

A US Pentagon official confirmed on Wednesday that Russia was believed to have moved short-range nuclear weapons, and said it was part of a "disturbing trend" that raised questions about Moscow's commitment to pledges it has made on arms control.

"This is one of a number of issues of concern," said the Pentagon official, who spoke on condition of anonymity.

This report can only be a political provocation

Anatoly Lobsky, Russia's Baltic Fleet

The US has said it plans to talk to Russia about the reports.

Russian Defence Ministry sources denied the report, according to the Interfax news agency.

"This report can only be a political provocation," said Anatoly Lobsky, a spokesman for Russia's Baltic Fleet.

Weapons agreement

The Washington Times, which first reported the story, quoted unnamed US intelligence officials.

It said the movement of the new battlefield nuclear arms to Kaliningrad, a Baltic Sea port located in a Russian enclave between Poland and Lithuania, had been detected in June.

But the movement was not reported in an internal US Defence Intelligence Agency report until December, it said, citing the same unidentified officials.

The officials said the movement was "a sign Moscow is following through on threats to respond to Nato expansion with the forward deployment of nuclear weapons".

Russia and the US have a non-binding agreement to reduce arsenals of tactical nuclear weapons. In November Russian President Vladimir Putin proposed that both countries cut their nuclear arsenals to 1,500 warheads each.