The feud, one of many over issues as diverse as culture, pollution and borders in the region of 600 million people, adds to the difficulties leaders face in trying to turn Southeast Asia into a unified economic community by 2015.

Malaysian efforts to promote the Tor-tor folk dance and Gordang Sambilan drum performance - both with origins in Sumatra - as its own cultural heritage sparked protests this month in Jakarta, where a group torched Malaysia's flag and threw stones at its embassy. The violence was a sharp contrast to the Tor-tor itself - a gentle, traditional dance featuring a mix of subtle hand and leg movements.

Malaysia's government summoned Indonesia's acting ambassador for talks on Monday to express its concern over the violence.

Government officials on both sides have tried to calm the situation, saying it is a misunderstanding over plans to promote the culture of the Mandailing people, who live in both Sumatra and across the narrow Malacca Strait in mainland Malaysia.

Malaysia and Indonesia share deep Islamic and cultural ties that go back centuries. The Malay and Indonesian languages are mutually intelligible and historians say they originate from Indonesia's Riau islands, just south of Singapore. But subtle differences do exist and could be part of the reason for the latest row. The Malay word for heritage, "warisan", carries a stronger connotation of ownership in Indonesian.

FOLK MUSIC, BATIK, AND CURRY

The case has touched a raw nerve in Indonesia, which has previously argued with Malaysia over who claims the rights to folk music, batik textiles and spicy beef Rendang curry.

In recent years, allegations of poor treatment of the hundreds of thousands of Indonesian maids who cook, clean and care for children in smaller, richer Malaysia have soured ties. Jakarta stopped sending domestic helpers to Malaysia in 2009 after numerous cases of abuse, only lifting the ban this month after Malaysia set stricter rules for employers of maids.

"Indonesians are jealous that Malaysians have a better standard of living and it does seem that Malaysians - and especially the Malay ethnic group - tend to look down their noses at their Indonesian brethren," said Keith Loveard, who heads political risk analysis at Concord Consulting in Jakarta.

The neighbours fought a border war in the 1960s on the island of Borneo, and some in Indonesia still seem in a fighting spirit.

"Malaysia is a small country. It would only take us five days or a week to burn it," said an executive in Jakarta originally from Sumatra, who declined to be identified because of the sensitivity of the issue.

The Batak people of Sumatra, a related ethnic group to the Mandailing, have a reputation in Indonesia as argumentative. A local joke goes that in law courts it's common to find that lawyers and those on trial are all Batak.

While any real conflict is very unlikely, nations in the region have been stepping up defence spending in recent years, as fears grow over China's military and posturing between it and Southeast Asian countries over ownership of oil-rich islands in disputed waters north of Borneo.

Thailand and Cambodia fought a deadly border skirmish over a disputed ancient Hindu temple last year, an issue that the Association of South East Asian Nations struggled to mediate, underlining its troubles in fostering genuine unity.

MORE HIP-HOP THAN TOR-TOR

While anger will soon dissipate, a common sentiment heard in Indonesia is simply disappointment that Malaysia feels the need to "steal" its culture. From the Malaysian perspective, it is simply about preserving culture that is in danger of dying out.

"Recognising these two cultures under the act doesn't mean that it is being 'claimed' and owned by Malaysia. What we hope is, through the registration of the cultures, they can be preserved and widely promoted," said Ramli Abdul Karim Hasibuan, president of the Mandailing association in Malaysia.

Scholars say the Mandailing people in Malaysia did not resist colonial British attempts last century to label them as Malay, which led to their culture evaporating, whereas traditions have been preserved better in Sumatra, Indonesia's largest island and full of different ethnicities.

The younger generation, more likely to dance to hip-hop than the Tor-tor, is more concerned about who wins between Malaysia and Indonesia on the soccer pitch, though haze pollution in Kuala Lumpur from Indonesian land-clearing fires is a real irritant.

"Keep your dances and your culture. While you're at it, keep your haze to yourself too," said Twitter user @mediha_m, responding to Indonesians on the social media site lambasting Malaysia's cultural poverty. (Additional reporting by Rachel Will, Angie Teo, Niluksi Koswanage and Siva Sithraputhran in KUALA LUMPUR; Editing by Stuart Grudgings and Nick Macfie)

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