KUALA LUMPUR (Reuters) - Malaysia's debt-laden state fund 1Malaysia Development Bhd (1MDB) said on Sunday that it has not been contacted by the Swiss authorities but is ready to assist in any investigation if approached.

Switzerland's Office of the Attorney-General on Friday said it had opened criminal proceedings relating to 1MDB, which involved "suspected corruption of public foreign officials, dishonest management of public interests and money laundering".

"We remain committed to fully cooperate with all lawful authorities that are currently investigating 1MDB," 1MDB said in a short written statement.

1MDB, whose advisory board is chaired by Prime Minister Najib Razak, has been dogged by controversy over its US$11 billion (S$15.5 billion) debt and is being examined by the authorities investigating accusations of financial mismanagement and graft.

Datuk Seri Najib is trying to reassert his leadership over his government and a stumbling economy following severe criticism after being embroiled in the 1MDB scandal.

In July, the Wall Street Journal reported that investigators looking into 1MDB found that nearly US$700 million was deposited into Mr Najib's private bank account. Reuters has not verified the report.

The anti-graft agency has since verified the funds were a donation from the Middle East. It said on Aug 3 that it would ask Mr Najib to explain why the donation was deposited into his private account.

Mr Najib has denied wrongdoing and said he did not take any money for personal gain.