The Shanghai Cooperation Organization (SCO) member states should strengthen anti-terror cooperation to ensure regional security, Russian Prime Minister Dmitry Medvedev said here Wednesday.

Medvedev told the 11th SCO prime ministers' meeting should work together to face new challenges as the risk of a sliding world economy grew and the regional security situation became more complicated.

He said terrorism, ethnic separatists, and religious extremists were the "three evil forces" which threatened regional security.

Not only SCO members but observer countries should be actively involved in counter-terrorism operations, strengthen cooperation, and jointly eliminate the regional terrorist threat, he said.

The meeting opened here Wednesday, attended by leaders from the six SCO member states, China, Russia, Kyrgyzstan, Kazakhstan, Tajikistan and Uzbekistan, and representatives from five observer states, India, Mongolia, Iran, Pakistan and Afghanistan.