Chinese banks have written off more than $300 billion of bad loans in the past three years, an official said Thursday as Beijing seeks to reassure investors that the country can cope with its mounting debt problem.

The giant figure comes as Beijing has made getting credit cheap and easy in an effort to boost slowing growth in the world's second-largest economy.

But analysts have warned that a debt-fuelled rebound might be short-lived and ballooning borrowings risk sparking a financial crisis as bad loans and bond defaults increased.

Wang Shengbang, a high-ranking official with the China Banking Regulatory Commission (CBRC), said the country's banks had seen their non-performing loan ratios rise consistently for four and a half years, reaching 1.75 percent at the end of March.

But they were well-prepared to handle the losses, he said, adding domestic lenders had written off two trillion yuan ($304 billion) of bad loans over the past three years.

"Current figures show the banking sector's operation is generally stable and the risks are under control," he told reporters at a briefing.

"The CBRC took precaution measures in advance and in 2011... required banks to set aside more in provisions while the economy was in an upturn cycle so that we were able to accommodate huge write-downs when the economy was in a downturn cycle," he said.

China's total debt hit 168.48 trillion yuan at the end of last year, equivalent to 249 percent of the national GDP, top government think tank the China Academy of Social Sciences (CASS) has estimated.

The most worrying risks lie in the non-financial corporate sector, particularly in state-owned enterprises (SOEs), Li Yang, a senior CASS researcher said last week.

But none of the officials at Thursday's briefing -- from the central bank, finance ministry, and national planning agency -- addressed questions about SOE debt levels, with the moderator referring the issue to the "relevant authorities".

China's government debt ratio was 41.5 percent of GDP at the end of 2015 if contingent debt -- obligations that authorities are not liable for at present, but could become responsible for -- was included, said Wang Kebing of the finance ministry.