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Vincent Thian, Associated Press
Malaysian Prime Minister Najib Razak pauses during a government event in Putrajaya, Malaysia, Wednesday, July 8, 2015. Malaysian authorities have frozen six bank accounts as part of an investigation into allegations that hundreds of millions of dollars were transferred from a state investment fund to the personal accounts of Najib.

KUALA LUMPUR, Malaysia — Malaysian authorities raided the office of state investment fund 1MDB on Wednesday as part of an investigation into allegations that hundreds of millions of dollars were funneled from the fund to the personal accounts of Prime Minister Najib Razak.

1MDB said in a statement it is extending full cooperation and provided documents and materials to investigating officers visiting its office.

The fund, which denied it gave money to Najib, said legal action should be taken if any wrongdoing is found.

The country's attorney general confirmed over the weekend that he had received documents from investigators that linked Najib and 1MDB.

The existence of the documents, which allegedly show $700 million was wired from entities linked to 1MDB into Najib's accounts, was first reported by The Wall Street Journal on Friday.

The documents sent to the attorney general pave the way for possible criminal charges and have embroiled Najib in the biggest crisis of his political career. Najib was already under increasing criticism over his leadership, particularly from his political mentor, former Prime Minister Mahathir Mohamad.

On Tuesday, authorities froze six bank accounts and seized documents related to 17 accounts at two banks for further investigation. The attorney general's office released a statement Wednesday in which it said that none of the six accounts belong to Najib.

Meanwhile, Najib said his lawyers have sent a letter to The Wall Street Journal to verify if it was accusing him of misappropriating funds in its report. The confirmation is necessary to decide the next course of legal action, he wrote on his blog.

Najib said ongoing investigations must clarify whether the documents are genuine and reiterated that he has never taken any money from 1MDB for personal gain.

The investment fund, set up by Najib in 2009 to develop new industries, has accumulated 42 billion ringgit ($11 billion) in debt after its energy ventures abroad faltered. Critics, led by Mahathir, have voiced concerns about 1MDB's massive debt and lack of transparency.

The Wall Street Journal report said five deposits were made into Najib's accounts and that the two largest transactions, worth $620 million and $61 million, occurred in March 2013 ahead of a general election.

National police chief Khalid Abu Bakar said investigators will also question The Wall Street Journal about the confidential banking documents. He said the leak of the documents was "tantamount to economic sabotage."

If charged, Najib would be the first Malaysian prime minister to face a criminal prosecution. His ruling National Front coalition has been in power since independence from Britain in 1957. However, support for the coalition has eroded in the last two general elections. In 2013, it won the polls but lost the popular vote for the first time.