Mr Koizumi is head and shoulders above his rivals

Mr Koizumi, who has held the post for two and a half years, garnered 399 votes - 260 more than his closest rival.

He had been strongly favoured to defeat his three challengers - Shizuka Kamei, a senior party executive, Takao Fujii, a former transport minister, and Masahiko Komura, a former foreign minister.

The BBC's Jonathan Head in Tokyo says many conservative LDP members voted for him, against their deepest political instincts, realising that his charisma was an electoral asset.

Mr Kamei came second with 139 votes, followed by Mr Fujii with 65 and Mr Komura with 54.

"This election comes at a time of great change for the party," Mr Koizumi said as he accepted his second term as leader.

"This was an election to prove this party is the party of the people, and of promoting reforms."

KOIZUMI'S CHALLENGERS Shizuka Kamei, 66: former LDP policy chief; favours revising pacifist constitution and more public spending Masahiko Komura, 61: former foreign minister; wants less austere fiscal stance Takao Fujii, 60: former transport minister; wants more public spending, but with better focus How the vote works

Mr Koizumi is now expected to reshuffle his cabinet ahead of the next general election, likely to be held in November.

The LDP is the largest party in Japan's lower house, almost guaranteeing its leader the prime ministership.

Our correspondent says Mr Koizumi's flamboyant style and reformist agenda have unsettled the traditional party bosses.

He has faced criticism from some quarters for his slow progress in reviving the Japanese economy.

But many hardline conservatives backed him because they regarded his public popularity as vital to win the next general election.

Mr Koizumi's easy-going style has been on frequent display in recent weeks, from opening the pitching at a school baseball game to visiting many of the country's hard-pressed industries.

Under the election rules, the winner needed to win a majority of the 657 ballots available.

LDP MPs cast 357 votes, while the other 300 were calculated to reflect the votes of the party's 1.4m grass-roots members.