King George Tupou V of Tonga, who introduced democracy to the South Pacific archipelago after riots following his ascension in 2006, died in a Hong Kong hospital on Sunday, the Tongan government said on Monday.

He was 63. Tupou V's younger brother and the heir to the throne, Crown Prince Tupouto'a Lavaka, was with him when he died while on a visit to Hong Kong. A government statement confirming his death was read on local radio.

The New Zealand government, a major aid donor to Tonga, said he would be remembered for ushering in significant political change.

He believed that the monarchy was an instrument of change and can truly be seen as the architect of evolving democracy in Tonga. This will be his enduring legacy, said Prime Minister John Key in a statement.

Shortly after Tupou V ascended the throne in 2006, demonstrations demanding greater democracy turned into riots in which eight people died and large parts of the commercial centre of the capital, Nuku'alofa, were destroyed.

The Oxford-educated king then said he would relinquish most of his power in the last Polynesian monarchy to a broadly popularly elected government after 165 years of feudal rule.

The first elections in which citizens voted for the majority of the seats, outnumbering those elected by nobles, took place in November 2010.

Although political reform is not yet complete, his willingness to start is a very significant event, opposition member of parliament Akilisi Pohiva told Radio New Zealand International.

Tonga, which comprises 170 islands, has a population of about 100,000 and lies about 2,120 km (1,320 miles) northeast of New Zealand.

Its economy is dominated by tourism, fishing, growing crops, and earnings sent back by expatriates.

Tupou V, a flamboyant, bachelor king, was known for eccentricities, such as being driven around in a London taxi and his penchant for ornate and elaborate uniforms and top hats.

(Reporting by Mantik Kusjanto; Editing by Paul Tait)