While the ruling Barisan Nasional coalition has won a key by-election with an increased majority, analysts said it was only a temporary setback to former deputy premier Anwar Ibrahim's hopes of a triumphant return to politics.

The poll on Saturday in the semi-rural seat of Ijok in Selangor was widely touted as a litmus test of popularity for both sides ahead of a general election expected before 2009.

BN retained the seat against opposiiton Parti Keadilan Rakyat with an increased majority up 210 from the 2004 general election.

Anwar expressed disappointment after leading a spirited campaign for Keadilan, which his wife heads.

"I am sad for Malaysia," Anwar said in his initial reaction to the results.

"I have been talking about the fraudulent process all the while but I did not think it was going to be so bad ... intimidation and blatant bribery, the whole conduct of the election," he said.

Anwar promised to launch an official protest, bitterly alleging that the by-election was ridden with fraudulent conduct.

Deputy Prime Minister Najib Razak said the BN win cemented the people's confidence in the government.

"It was very fiercely fought, we faced everything that was thrown at us but at the end of the day, we prevailed," said Najib.

"It's a good precursor for the next general election," he said.

Setback for Anwar

Analysts had said PKR was unlikely to win the by-election, but had predicted a reduced majority for the BN, which has dominated Malaysian politics since independence in 1957.

"I was quite prepared to see BN winning even though the opposition put on a strong fight, but I was surprised that they (BN) had widened the margin," said Yang Razali Kassim, of the S Rajaratnam School of International Studies at Singapore's Nanyang Technological University.

Yang said the high voter turnout was a key factor that turned the tide in favour of the ruling coalition.

"It is a setback for Anwar but while he may be down, he's definitely not out yet. It's too soon to write him off at this point," he said.

The voter turnout in this hotly contested by-election is an unprecedented 83.08 percent - the highest in by-election history.

In the 2004 general election, the turnout in Ijok was 76.17 percent, or 9,411 voters. In this by-election three years later, a total of 10,195 voters cast their votes.

Of the nine polling districts, Malay-majority Bukit Badong scored the highest with 90.10%. Another five saw over 80% turnout.

The lowest turnout is in Indian-majority Tuan Mee, 79.9%, Chinese-majority Pekan Ijok, 75.1% and Chinese-majority Batang Bestari Selatan 68.6%.

Comeback bid

Anwar's campaign for Keadilan marked his first major contribution to Malaysia's political scene since his 1998 sacking by Mahathir.

"Anwar is determined to become prime minister at all cost and I believe he will continue to find ways and means to make himself relevant," said political commentator Chandra Muzaffar.

After Saturday's defeat, the charismatic leader, known for his fiery speeches, said he remained optimistic of his return to politics.

"It's a very good turning point and I was able to articulate our views, but we are dealing with a very dirty process," he said.