Exchange-traded funds designed to let investors play China's bond markets, which are mostly closed to foreigners, are facing a slow start amid concerns about mainland issuers' credit quality, high property prices and the slowing economy.

At more than $5 trillion, China's onshore fixed-income markets are outranked only by the U.S. and Japanese markets, and offer attractive rates.

But trading volumes for three Chinese bond ETFs launched in late 2014 have dwindled, and the ETFs are drawing assets at a much slower pace than a Chinese equities ETF run by Deutsche Bank, which since a November 2013 launch has attracted more than $1 billion in assets.

Analysts predict foreign fixed-income investment on the mainland will grow as China allows more foreign debt ownership. Investors are wary about China's shaky bond issuers, high real estate valuations, and slowing economy.

"If they were launched when there was not a global slowdown, from an economic perspective it might be a different story," said Dave Mazza, funds research chief at State Street Global Advisors.

Over the past 12 months the Standard & Poor's China Composite Select Bond Index has gained 8.47 percent. So far in 2015, the China index is up 1.9 percent. Total 2015 returns from the new ETFs range from zero to 1 percent.

Dennis Hudachek, analyst at in San Francisco, said it may take a while before investors are comfortable with mainland China credits, even among investors with holdings in the $100 billion 'dim sum' market of yuan-denominated bonds issued in Hong Kong.

Van Eck's ChinaAMC China Bond Fund was the first onshore debt ETF when it launched in November. It tracks the ChinaBond China High Quality Bond Index of fixed-rate, renimbi-denominated debt. Its net assets total $24.5 million, according to Lipper data.

Trading volumes peaked at 108,000 shares on Nov. 24, and have since declined more than 90 percent to well under 10,000 shares a day, according to Thomson Reuters.

KraneShares EA Fund China Commercial Paper ETF has about $22 million in assets, and trades less than 1,000 shares a day.