Mr Koizumi (R) is well ahead of Katsuya Okada (L)

According to polls in three Japanese papers, the LDP has a lead of around 20 percentage points over its main rival, the Democratic Party of Japan (DPJ).

The Asahi Shimbun said the LDP would win at least 241 seats, giving it and its coalition partner a clear majority.

Prime Minister Junichiro Koizumi said he felt a "good response" from voters.

Mr Koizumi sees the election as a referendum on his reform programme, which was blocked by rebels within his own party.

KEY NUMBERS 480 lower house seats 241 needed for a majority LDP held 249 in last term But lost 37 MPs over postal reform row Its coaltion partner, New Komeito, has 34 seats

One paper, Yomiuri Shimbun, said that for single-seat constituencies, 42% of those surveyed planned to vote for the LDP, while 20% supported the DPJ.

Before the election was called, the LDP had 249 seats in the 480-seat lower house and its coalition partner the New Komeito had 34. The DPJ had 175.

Koizumi upbeat

Mr Koizumi called the snap election following the defeat in the upper house of his landmark proposals to reform the country's postal system.

Voters' voices

The prime minister had made post office privatisation the cornerstone of the economic reforms he has pursued since taking office in 2001.

On Friday he told reporters: "We will beat out certain elements who have ravaged politics in an attempt to protect their own vested interests."

Proponents of the reforms say they are urgently needed to put the postal service's massive deposits into the hands of private investors and provide an impetus to the economy.