Rising corporate debt levels in Asia could make investors nervous after missed debt payments by one of Portugal's conglomerates spurred renewed fears over debt defaults.
"It's not so much the [debt] level of individual companies that raises concern," Wilfried Verstraete, CEO of Euler Hermes, the trade-finance insurance arm of Allianz, said in an interview. "What might be more of a concern is the balance sheets of banks themselves."
If regional banks restrict lending because of excessive bad loans or because of monetary tightening, as is currently the case in China, it can tighten the noose on some companies, he said.
Read More Here's what's happening in Portugal
"Never forget that the definition of a bankruptcy is when you don't have the liquidity to pay your debts," he said. "If the banks suddenly no longer provide the necessary liquidity, you're in trouble."
The inability of Portuguese conglomerate Espirito Santo International to make some of its short-term debt payments has fueled concerns one of its units, Portugal's leading bank, Banco Espirito Santo, might default on its debt.
The region's banks and governments are considered too closely knit, so that had a knock-on effect on Portuguese government bonds, and with memories of the European credit crisis still fresh, spurred fears of "doom loop" around the continent.
Within Asia, corporate borrowing picked up in recent years. Data from the Bank for International Settlements show international corporate bond issuance from 2010 to the first half of 2013 was up over 133 percent by China companies, while India and Korea saw around 39 percent and 21 percent increases respectively, with the rest of Asia seeing a more than 54 percent increase.
While many analysts believe contagion from Portugal is unlikely, Asia's companies may face knock-on effects from a credit issue closer to home: China's Qingdao port is investigating whether cargos of metal were used and re-used as collateral to obtain financing from different banks and trading houses, possibly leaving banks and firms around the region holding the bag.
In these types of cases, the main risk isn't the payment default by the company abusing collateral, it's the domino effect on subcontractors and suppliers, which will also not be paid, Verstraete said.
To be sure, Euler Hermes' own data show Asian insolvencies will likely remain relatively low in 2015, down around 19 percent from 2007, despite a slight increase in numbers in China. Globally, the company expects insolvencies to continue to decline from global financial crisis highs, but to remain well above the levels seen in 2007.
But Verstraete notes that while the probability of default in Asia may be falling, the payment risks could be rising.
"Trade within the Asian region is increasing tremendously, which means that a lot of people are currently trading with partners they've never traded with before," he said. "It just increases the uncertainty of getting your bills paid on time."
Others are also concerned that the data may not fully present the debt risks within Asia.
"In aggregate, corporate leverage doesn't appear to be anywhere near the level seen at the onset of the Asian Financial Crisis," with debt-to-equity ratios among listed firms still mostly lower than in 1996, Frederic Neumann, an economist at HSBC, said in a note Friday.
But he noted many smaller, unlisted companies have seen substantial debt build-ups. Since they mostly seek financing from banks rather than the bond market, it's difficult to ascertain their leverage ratios, Neumann said.
"What complicates the matter as well is that some of this borrowing may carry explicit or implicit sovereign guarantees, which makes it harder to assess the true risk profile of this borrowing," he noted.
But while how risky the borrowing truly is may be an open question, "activity in Asia remains in large part credit driven. That process is only sustainable for so long," Neumann said.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1