BEIJING, Oct 16 - China's defense minister struck a conciliatory tone with Southeast Asia defense chiefs on Friday, saying that all needed to work hard to maintain peace and stability against threats, including instigation by foreign forces using social media.

China's relations with several Southeast Asian countries, especially the Philippines and Vietnam, have been strained over Beijing's increasingly assertive tone in pushing territorial claims in the disputed East Vietnam Sea.

China has overlapping claims with Vietnam, the Philippines, Malaysia, Taiwan and Brunei in the East Vietnam Sea, through which $5 trillion in ship-borne trade passes every year.

Chinese Defence Minister Chang Wanquan told his counterparts from all 10 members of the Association of South East Asian Nations (ASEAN) at the start of an informal summit in Beijing that all needed to push for the "correct" development of ties.

Chang said the biggest common need was to maintain stability.

"At present the regional situation is generally stable, but there are obvious downward economic pressures and non-traditional security challenges are increasing," he said, pointing to the threat from terror groups.

"Forces from outside the region are using the Internet, social media and other means to carry out incitements against countries in this region, threatening social stability," Chang said, without elaborating.

China says it faces a threat from Islamist militants in its far western region of Xinjiang, who it says often use the Internet to spread propaganda, link up with groups outside of China and encourage attacks.

Chang added that China is willing to work with ASEAN to boost military cooperation and jointly maintain regional peace and stability.

He made no direct mention of the East Vietnam Sea in front of reporters, who were only allowed to listen to the first few minutes of his opening remarks.

China stepped up the creation of artificial islands in the East Vietnam Sea last year, drawing strong criticism from Washington.

Media reports say the United States has decided to conduct freedom-of-navigation operations inside 12 nautical-mile limits that China claims around islands built on reefs in Vietnam’s Truong Sa (Spratly) archipelago.

China denies it has militarized the East Vietnam Sea, saying construction work is mostly for civilian purposes, and has warned that Beijing would not stand for violations of its territorial waters in the name of freedom of navigation.

The United States says that under international law building up artificial islands on previously submerged reefs does not entitle a country to claim a territorial limit and that it is vital to maintain freedom of navigation.