'I would like to say 'sorry' to all South Koreans. I cannot apologise enough to my children and the people of this country.' - THE SUSPECT (above), known only by his family name Chae, under police escort after his arrest at a Seoul police station.

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His act on Sunday reduced the stone and wood structure Namdaemun, or 'Great South Gate', to a charred hulk.

The suspect, a convicted arsonist identified only by his family name Chae, told police he had planned the mischief for several months.

On Sunday, he poured a bottle of paint thinner on the floor of the wooden structure and left two other bottles nearby before setting it on fire with a disposable lighter, police said.

'I would like to say 'sorry' to all South Koreans. I cannot apologise enough to my children and the people of this country,' Chae told a group of reporters at a police station.

He was arrested late on Monday on Ganghwa Island, west of Seoul, and was held for questioning overnight at police headquarters in the capital.

District police chief Kim Young Soo told a news conference yesterday that the suspect had complained of not getting enough compensation a decade ago from developers for about 100 sq m of his residential land in Gyeonggi province, near Seoul.

'The arsonist said he committed the crime out of anger because he felt the government did not take enough care with the appeal he filed after being insufficiently compensated for redevelopment in his residential area,' Mr Kim said.

It was for the same reason that the suspect committed arson in 2006, destroying part of the Changgyeong Palace, a World Heritage site.

He was given a suspended jail term and fined 13 million won (S$19,500). He was released from a detention centre later that year, said Mr Kim.

On Sunday, a 'grudge' over the fine and the land dispute caused him to strike again. He said he picked the 610-year-old landmark because it was easily accessible, according to police.

The arsonist's family apologised to the nation yesterday.

'My dad has had a deep grudge about compensation, often talking about 'bad guys' in his sleep. But it was too much...to burn the nation's assets,' said his daughter.

The Namdaemun - a pagoda-style two-storey wooden building on a stone base - was the southern gate in the walls that surrounded Seoul during the Chosun Dynasty of 1392-1910.

It was built in 1398, rebuilt in 1447 and renovated several times after, but still contained some 600-year-old timbers.

The Cultural Heritage Administration said it would take at least three years and some 20 billion won to fully restore the gate.

Hundreds of South Koreans have gathered near the badly charred structure since Sunday to mourn the loss of the national treasure, as several dozen police and workers stood by.

'My heart is burning,' Mr Lee Il Soo, 56, said as he fought back tears. He said the fire destroyed the pride of South Korea.

ASSOCIATED PRESS, REUTERS