* SSEC +0.3 pct, CSI300 +0.5 pct, HSI +0.6 pct
* Premier Li says China able to keep markets stable
* China cyber-security stocks surge after global cyber attack
SHANGHAI, May 15 (Reuters) - China stocks, which had fallen for five weeks in a row, firmed on Monday morning after the government soothed market fears of tighter regulation, saying risks in the banking sector were "completely controllable."
But the upbeat sentiment - also aided by surges in cyber-security stocks after the global cyber attack at the weekend - was capped by China's disappointing factory activity and investment data that deepened worries of renewed economic slowdown.
Hong Kong stocks followed Asian markets higher as investors shrugged off threats posed by the ransomware attack, a missile test by North Korea, and weak U.S. data.
The CSI300 index rose 0.5 percent to 3,401.53 points by the lunch break, while the Shanghai Composite Index gained 0.3 percent to 3,092.28 points.
Chinese stocks sank to seven-month lows last week in a five-week losing streak, as a coordinated campaign among financial regulators against shadow banking and risky, leveraged investments drove up market rates and dented investor confidence.
But in an apparent effort to settle market nerves, China's banking regulator said on Friday that risks in the banking sector were completely controllable, and the market did not have to be nervous of scrutiny.
In addition, Chinese Premier Li Keqiang said on Sunday that China would strike a balance between financial stability, gradual deleveraging, and steady economic growth, noting that China was capable of maintaining stability in its financial markets.
Such market-friendly language helped offset economic concerns triggered by news that China's factory output and fixed asset investment growth cooled more than expected in April.
Most sectors rose on Monday, but the property sector continued to sag amid tighter real estate curbs.
Shares of cyber-security stocks were in the spotlight after the global cyber attack over the weekend, with more than 10 stocks in the sector, including Venustech Group, Bluedon Information Security Technologies and Nsfocus Information Technology jumping by the daily 10 percent limit.
The Hang Seng index added 0.6 percent to 25,301.50 points, while the Hong Kong China Enterprises Index gained 1.2 percent to 10,409.63.
UBS pointed to signs of mainland Chinese investors diversifying away from domestic exposure.
"We have observed southbound investors showing increased interest in non-Chinese HK shares, which may indicate their intent to diversify and avoid the domestic spill-over effect," UBS strategist Gao Ting said.
(Reporting by Luoyan Liu and John Ruwitch; Editing by Eric Meijer)