BIS' annual report said that taken at face value, indications suggest borrowers in China are especially vulnerable.

China's credit-to-GDP gap, which captures excess credit activities relative to GDP, reached 23.6, and the debt service ratio stood at 9.4 by the end of 2013, according to BIS, which has branches in Switzerland and Mexico. These indicators signal booming credit in China.

Official data of SAFE said that by the end of 2013, China's foreign debt ratio was 35.59 percent, debt service ratio was 1.57 percent, while short-term external debt to foreign exchange reserve ratio was 17.71 percent.

All the credit health indicators are within the safety line, according to a circular released by SAFE on March 31.

Current low default rates and high yields have attracted investors and banks to lend to China's enterprises, while overseas funding channels' relatively cheap funding costs appeal to Chinese firms.

In the Asian market, high-yield bonds issued by Chinese enterprises get relatively high ratings, Moody's Investors Service said at a recent forum on bonds in Shanghai. By April, about 54 percent of high-yield bond-issuing enterprises in Asia were on the Chinese mainland, and many are in the pipeline to issue bonds, half of which are realty developers, Moody's Investors Service said.

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