Jointly led by Russia and China, the Shanghai Cooperation Organisation (SCO) was launched in 2001 to combat radical Islam and other security concerns in their own countries and across Central Asia.
It added two new members, India and Pakistan, last year and Iran has been knocking at the door. Tehran is currently an observer rather than a full member of a bloc that also includes four ex-Soviet Central Asian republics.
"One of the pressing tasks facing the SCO is to continue fighting against militants of the Islamic State who, following the extremist group's defeat in Syria and Iraq, have returned to their native countries, some of which are SCO members or observers," China's official Xinhua news agency said this week.
Member countries have destroyed more than 500 training bases for armed militants and arrested some 2,000 members of "international terrorist organisations" between 2013 and 2017, it said.
China says it faces a threat from Islamist militants in its far western region of Xinjiang, where hundreds have been killed in unrest in recent years.
China has long found a sympathetic audience from Russia and Central Asian countries for its security crackdown, although Western nations have expressed concern about rights abuses, charges China denies.
The Saturday-Sunday summit in the northern Chinese port city of Qingdao comes ahead of an historic planned meeting next week between North Korean leader Kim Jong Un and U.S. President Donald Trump in Singapore.
Kremlin foreign policy aide Yuri Ushakov told reporters this week the Korean peninsula would be discussed between Putin and Chinese President Xi Jinping, who meet first in Beijing on Friday, although he gave no details.
Underscoring China's close ties with Russia, Xi is likely to award Putin the country's first friendship medal.
Xinhua said Xi will give out the medal on Friday afternoon at the Great Hall of the People, and while it did not name the recipient the time coincides with Xi's formal talks with Putin in the same venue.
The attendance of Iranian President Hassan Rouhani also offers China and Russia an opportunity to reaffirm their commitment to the Iran nuclear deal. Trump withdrew the United States from the 2015 deal last month.
However, Chinese Foreign Ministry spokeswoman Hua Chunying said they did not want Iran overshadowing the summit.
"We hope all parties focus on the theme of the summit," she said.
Serious disagreement among members remains, even if it is usually hidden from view behind diplomatic language on which everyone can agree, such as what China calls the "three evil forces of terrorism, separatism and extremism".
India and Pakistan remain deeply suspicious of each other, and China has long held off from strong public backing for Russia over Ukraine.
"The traditional hostility between India and Pakistan could affect the efficiency of the SCO's decision-making process," Sun Zhuangzhi, head of the SCO Research Centre affiliated to the Chinese Academy of Social Sciences, wrote in the official China Daily.
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