importance" of a 10-year-old declaration on the conduct of the parties (DOC) pledging to promote peace and understanding in the disputed area.
"We stressed the need to intensify efforts to ensure the effective and full implementation of the DOC based on the guidelines for the implementation of the DOC," the leaders said in a statement at the end of the two-day summit.
China and several ASEAN countries have rival claims to uninhabited islands in the sea, which is believed to be rich in hydrocarbons and straddles strategic shipping lanes vital to global trade.
The United States claims a "national interest" in keeping the sea open for trade and has recently stepped up military cooperation with the Philippines, one of the claimants, as part of its foreign policy "pivot" to Asia.
China has competing territorial claims in the sea with ASEAN members Brunei, Malaysia, the Philippines and Vietnam.
US naval commanders have repeatedly said they are concerned about minor incidents, such as recent clashes over fishing rights and energy exploration near the uninhabited islands, blowing up into major regional conflicts.
Chinese President Hu Jintao visited Cambodia on the eve of the summit in what many analysts took to be a form of pressure on Phnom Penh to use its chairmanship to slow down the South China Sea negotiations.
Philippine Foreign Secretary Albert del Rosario said there was a "big disagreement" on Tuesday over whether to invite China to help draft a code of conduct, designed to prevent small incidents in the sea from escalating.
Cambodia, which holds the ASEAN chair in 2012, is eager to bring China into the drafting process but the Philippines, Thailand and Vietnam say the bloc's members should draft a code among themselves before presenting it to Beijing.
Cambodian Prime Minister Hun Sen used his closing press conference to angrily reject reports of a rift over how to proceed in the negotiations with China.
He also denied he had tried to pull the issue off the agenda of the bloc's summit.
"Maybe some people think that during the ASEAN summit there is a difference of view between ASEAN and China. That is the wrong thinking," he said, adding that all parties were committed to peacefully resolving the disputes.
"What I hate the most is that they talk about Cambodia (being) under the pressure of China. Cambodia is the chairman of ASEAN and Cambodia has the right to set the agenda," he said through a translator.
ASEAN comprises Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam -- a grouping of nearly 600 million people from disparate economic and political systems.
The leaders called for restraint over a planned rocket launch by nuclear-armed North Korea later this month.
"We urged all parties concerned to exercise self-restraint and not to undertake any steps which could lead to the escalation of tensions in the Korean Peninsula," they said in a joint statement.
Pyongyang sparked alarm in the region when it announced last month it would launch a rocket to place a satellite in orbit.
The United States, Japan and other nations say the launch is a disguised ballistic missile test, and would breach a UN ban on North Korean missile launches.
The talks have also focused on historic by-elections in Myanmar, formerly known as Burma, which gave pro-democracy leader Aung San Suu Kyi a seat in parliament for the first time.
The leaders repeated a call made Tuesday for Western sanctions to be lifted in light of the elections, which Myanmar President Thein Sein praised as being "held successfully".
"We called for the lifting of all sanctions on Myanmar immediately in order to contribute positively to the democratic process and economic development of that country," the joint statement said.
Philippine President Benigno Aquino told reporters: "We have to show the people who are reforming in Myanmar that the road they chose is the right road. There has to be a reward."
ASEAN has often been dismissed as a talking shop but it has assumed new strategic importance in light of the economic and military rise of China in recent years.
In a step welcomed by some ASEAN members but which has irked China, the United States is deploying up to 2,500 Marines to northern Australia. The first 200-odd of the Marines arrived in Darwin on Wednesday.