Big Japanese insurers have stopped covering firms against riots in China, a report said Friday, a move seen likely to hit investment there as the countries remain stuck in a festering territorial row.

Major non-life insurers, including Tokio Marine and Nichido Fire Insurance, had been selling policies that cover damage from strikes, riots and civil commotion

But they have stopped accepting new applications for such riders or requests for expanded coverage since protests targeting Japanese businesses erupted in cities across China, the Nikkei newspaper said.

Tens of thousands of demonstrators have rallied across China to vent their anger over Tokyo's nationalisation of islands in the East China Sea known as the Senkakus in Japan and the Diaoyus in China.

Some protests turned violent, with Japanese shops and factories often the target, forcing firms to shut or scale back production.

The companies are evaluating the extent of damage suffered by existing policy holders, the Nikkei said.

An official at an unnamed major insurer said the firm will probably not begin accepting applications again until the beginning of next year at the earliest, the business daily added.

The Nikkei warned: "This is likely to affect Japanese companies as those that launch businesses in China will be uninsured against riots for the time being."

The number of Japanese firms operating in China topped 14,000 as of the end of August, the daily said, quoting a Japanese research institute.

Insurance claims related to the protests may reach about 10 billion yen ($126 million), according to General Insurance Association of Japan Chairman Yasuyoshi Karasawa.