CAPE TOWN, South Africa (AP) — The US ambassador to South Africa accused the country Thursday of providing weapons and ammunition to Russia for its war in Ukraine via a cargo ship that docked secretly at a naval base near the city of Cape Town for three days in December. South African President Cyril Ramaphosa said an investigation was underway.

Ambassador Reuben Brigety said the US was certain the equipment was loaded onto the Russian vessel at the Simon’s Town naval base and then transported to Russia, according to reports of his comments carried by multiple South African news outlets.

Ramaphosa was in Cape Town answering questions in Parliament when news of Brigety’s comments broke. When a lawmaker asked about the weapons and ammunition, the president replied that “the matter is being looked into, and in time we will be able to speak about it.”

Ramaphosa declined to comment further, citing the need for an investigation to play out.

The leader of the political opposition, John Steenhuisen, asked the president if South Africa was “actively arming Russian soldiers who are murdering and maiming innocent people?” Steenhuisen also asked if Ramaphosa could confirm that “weapons of war” were loaded onto the Russian ship.

Ammunition supplies have become a problem for Russia in the war. The leader of Russian military company Wagner complained last week about his mercenary soldiers in Ukraine allegedly dealing with dire shortages.

In a statement issued later Thursday, Ramaphosa’s office acknowledged a Russian ship named the Lady R docked in South Africa, but the office did not say where or what the purpose of the stop was.

The statement criticized the American ambassador for going public and said there was an agreement that US intelligence services would provide whatever evidence they have to aid South Africa’s investigation.

The Lady R and a Russian company tied to it, Transmorflot LLC, were sanctioned by the US last year following Russia’s invasion of Ukraine for being involved in the transportation of military equipment and weapons.

Brigety said earlier Thursday that South Africa’s alleged arming of Russia during its invasion of Ukraine was “extremely serious” and called into question South Africa’s supposed neutral stance.

“Among the things we (the US) noted was the docking of the cargo ship in the Simon’s Town naval base between the 6th and 8th December 2022, which we are confident uploaded weapons and ammunition onto that vessel in Simon’s Town as it made its way back to Russia,” Brigety was quoted as saying at a press conference in the South African capital, Pretoria.