A huge Russian container ship carrying a deadly explosive cargo seven times the amount that caused a massive explosion in the Middle East is stranded off the coast of Norway.

MV Ruby, a Maltese flagged ship, is reportedly carrying 20,000 tonnes of ammonium nitrate and according to Danish publication Nyheder, it has sustained cracks to the hull and a damaged rudder.

In 2020, less than 2,700 tonnes of ammonium nitrate stored incorrectly in Beirut, Lebanon, caused an enormous explosion that destroyed part of the city and left a crater in the harbour.

Tracking on the shipping site MarineTraffic shows the Ruby still in the same position off the southern Norwegian coast and west of Denmark.

It's reported the vessel has been seeking access to navigate the entrance waters of the Baltic Sea around Denmark on a voyage to Lithuania to make repairs.

But several ports and Scandinavian authorities are understood to have refused access after the ship suffered dangerous damage to the hull and rudder on August 22 when it ran aground shortly after leaving the port of Kandalaksha, Russia.

Danish authorities require the vessel to have a pilot, a person trained to navigate certain stretches of water, and a tug boat escort because of the dangerous cargo it carries.

Spokeswoman Anne Heinze, from the company DanPilot which provides shipping pilots in the region, said: "The vessel will not have a pilot tonight, and the last I heard it was in Norwegian waters."

The Danish Maritime Authority has said it is "aware" of MV Ruby amid warnings of a Russian "shadow fleet" of poorly maintained cargo and oil ships that have been active since the war with Ukraine began.

Senior analyst Jacob Kaarsbo from the think tank Europe calls Ruby's behavior "suspicious" after the ship stayed close to a NATO base at the Norwegian city of Tromsø and at oil and natural gas installations at Bergen, also in Norway.

Under extraordinarily tight security, Ukrainian President Volodymyr Zelensky visited a Pennsylvania ammunition factory in the US on Sunday that is producing one of the most critically needed munitions for his country's fight to fend off Russian ground forces.

The Ukrainian leader is in the United States seeking to unveil his "victory plan" for bringing an end to the war with Vladimir Putin's Russia.