BEIJING - The scale of the ongoing "Peace Mission 2014" joint military drill is the largest to date, a Chinese Defense Ministry spokesperson said on Thursday.

The exercise is being held from Aug 24 to 29 at Zhurihe training base in Inner Mongolia Autonomous Region, in accordance with the 2014-2015 defense ministry cooperation plan among Shanghai Cooperation Organization (SCO) members.

Spokesperson Yang Yujun told a regular news briefing the drill is progressing smoothly, with troop exercises beginning Friday.

Yang said the exercise will play an important role in deterring the "three evil forces" of terrorism, separatism and extremism, safeguarding regional peace and stability and improving the military's ability to coordinate fights against terrorism.

The exercise is the fifth multinational drill under the SCO framework. Kazakhstan, China, Kyrgyzstan, Russia and Tajikistan sent armed forces by land and air in early August.

Founded in Shanghai in 2001, the SCO groups China, Kazakhstan, Kyrgyzstan, Russia, Tajikistan and Uzbekistan. Afghanistan, India, Iran, Mongolia and Pakistan are observers. Belarus, Turkey and Sri Lanka are dialogue partners.