ATM cash machines outside a branch of the Royal Bank of Scotland in Edinburgh. Getty Images

Royal Bank of Scotland has become embroiled in the global investigation into alleged corruption relating to Malaysia's state investment fund, 1MDB, with the Swiss financial watchdog opening a probe into the lender, according to two people familiar with the matter. The Swiss authorities have launched an inquiry in relation to "certain client accounts held with Coutts," the former Swiss-based arm of RBS's private bank, the bank disclosed on Friday, adding that it is also co-operating with regulators in other countries in relation to the same accounts. The people said both statements referred to accounts connected to alleged wrongdoing in Malaysia. RBS sold Coutts International to Union Bancaire Privée last year but the bank said on Friday that Finma's enforcement proceedings were focused on the period when it still owned the Swiss private bank.

Switzerland's attorney-general said in January he had found "serious indications" that at least $4bn had been misappropriated from Malaysian state companies, following a criminal investigation related to 1MDB. The affair has rocked Malaysia's ruling elite, and embroiled the prime minister Najib Razak, who chairs 1MDB's advisory board. More from the Financial Times:

Malaysia's 1MDB in default as Abu Dhabi dispute escalates

Singapore charges former private banker with money laundering

1MDB dispute intensifies as Abu Dhabi ends relationship

Swiss authorities say a small portion of the $4bn was transferred to accounts held in Switzerland by former Malaysian public officials, and former and current officials from the United Arab Emirates.

Those familiar with the situation told the Financial Times that two payments totaling $860m were made between September 2009 and September 2010 from 1MDB to an account in Coutts' Zurich branch, known as the Good Star account. Finma has said it is investigating four financial groups over 1MDB but has declined to name them. A spokesman declined to comment. A former private banker for Swiss bank and wealth manager BSI was charged with money-laundering in Singapore following an investigation linked to the broader 1MDB probes. BSI says it is committed to anti-money laundering controls and is co-operating with regulators. Another ex-BSI banker who is under investigation in Singapore formerly worked at Coutts, according to people familiar with the situation.