Mainland China shares saw another day of volatile trade on Friday, falling as much as 7% at one point, as regulators announced an investigation.
The Shanghai Composite closed down 5.8% to 3,686.92, losing 12% for the week.
Mainland shares have seen several days of erratic trade this week, despite further moves by the Chinese securities regulator to calm the market.
On Thursday, the regulator said it would look into whether parties were mis-selling financial products.
Any criminal cases will be transferred to the police, the regulator said.
The benchmark Shanghai Composite has slumped about 25% since mid-June, its worst collapse in years.
In Hong Kong, the Hang Seng index closed 0.8% lower at 26,064.11 points.
Elsewhere in Asia
Shares elsewhere in Asia were down for most of Friday after a mixed jobs report from the US, which was described by analysts as "solid but far from great".
Employment in the US rose by 223,000 in June, while the April and May figures were revised down.
The data has dampened expectations for a US Federal Reserve rate hike in September.
In Tokyo, the Nikkei 225 share index closed flat, down just 0.08% at 20,539.79.
In Australia, however, the S&P/ASX 200 index closed down 1.1% at 5,538.30.
In Sydney, shares in Australia's national carrier, Qantas Airways, ended the day down 2.14% after the firm said it would pay a one-off bonus payment of about 90m Australian dollars ($68m; £43m) to employees affected by an 18-month wage freeze.
The payout will cover 28,000 employees, including those at subsidiary Jetstar, and is part of the workers' collective agreement, Qantas said on Friday.
The move comes after it reported its best half-year profit in four years.
While in South Korea, the benchmark Kospi index closed down 0.14% at 2,104.41.
The latest news on the Greek debt crisis was likely to temper investor sentiment on Friday, analysts said, after the International Monetary Fund (IMF) said Greece would need an extra €50bn ($55bn) over the next three years to stabilise its finances under the existing, disputed bailout plans.
The IMF also cut its forecast for Greek economic growth from 2.5% to zero.
Singapore-based business adviser Simon Littlewood from ACG Global told the BBC that investor sentiment was more likely to have fallen on concerns over Greece "and the uncertainty over a so-called 'Grexit'", rather than the US jobs data.
"There is a distinct concern over contagion in Europe," he said.
"The US job growth numbers are not spectacular enough to offset larger concerns in Europe and China."