JOHANNESBURG — South Africa's government insists it will allow a Russian oligarch to dock his superyacht in Cape Town, despite calls from the city's mayor to bar it.

The vessel, which is on its way from Hong Kong, belongs to Alexei Mordashov, an ally of Russia's Vladimir Putin who has been sanctioned by the EU and US.

The South African government said it is not bound by the sanctions.

But Cape Town's mayor said he has a "moral duty" to oppose Russia's "unjust war" and has vowed to block the yacht.

Mayor Geordin Hill-Lewis is a member of the opposition Democratic Alliance, which has urged the government to seize the 465ft (141m) yacht.

It is not clear how Cape Town officials plan to stop the vessel — called The Nord — from docking.

A spokesman for President Cyril Ramaphosa said: "South Africa has no legal obligation to abide by sanctions imposed by the US and EU."

"South Africa's obligations with respect to sanctions relate only to those that are specifically adopted by the United Nations," the spokesman, Vincent Magwenya, noted.

Accusing Geordin Hill-Lewis of "grandstanding", he added: "Municipal governments have no legal control over the country's borders."

Hong Kong's government recently offered similar justifications when refusing to prevent the entry of the $521 million (£472m) superyacht, with Chief Executive John Lee saying the city would be accountable to UN sanctions.

Western countries and their allies have imposed sanctions on more than 1,000 Russian individuals and businesses in response to Russia's invasion of Ukraine.

Like many other African countries, Ramaphosa's government has so far avoided directly criticizing Russia, abstaining in several UN votes that have expressly condemned the war. Pretoria has also called for a negotiated settlement to end the conflict.

On Monday, Geordin Hill-Lewis wrote on Twitter that there could be "no place in our city for accomplices to, and enablers of, Putin's war".

"Our country's foreign policy conduct in relation to Russia's illegal, imperialist war has been nothing less than shameful," he added in a further statement.

"Here is an opportunity to correct some of those errors of judgment and stand up for what is clearly right."

The luxury yacht is expected to arrive in Cape Town in the next few weeks, it is not known how long it will be allowed to stay.

Prior to the war, Mordashov was Russia's wealthiest man. The 57-year-old built a fortune of some $29.1billion (£25.92bn) through his steel and mining company Severstal.

Early in the conflict he was targeted by extensive Western sanctions because of his links with Putin. But the billionaire said he is not involved in Russian politics.

Mordashov has already lost one of his smaller vessels, the Lady M, to Western sanctions after it was seized by Italian police in March.

But The Nord is believed to be his biggest yacht. Forbes magazine describes it as one of the world's most extravagant boats.

Shortly after the outbreak of the conflict in Ukraine, the yacht — which features two helicopter pads, a swimming pool and a cinema — left the Seychelles for the far-eastern Russian port of Vladivostok. The move was seen as a bid to avoid the fate of the Lady M.

But experts said owners like Mordashov face serious issues finding international ports capable of maintaining superyachts. Most are in Europe, where the vessels would be instantly seized. — BBC