According to Myanmar police, five assailants including one armed with a knife attacked members of the National League for Democracy party (NLD) during an election campaign in the commercial capital Yangon on Thursday evening.

"One of the guys came out and started yelling at the car. He returned with two other men with machetes and attacked the people around the campaign truck," Aung Myo Oo, an NLD campaign manager who witnessed the attack, told Reuters news agency.

Four NLD members, including party candidate and sitting MP Nainggan Lin who was seriously injured, were taken to Yangon General Hospital for treatment.

Police said three of the five attackers had been arrested. The motive, however, remains unknown.

Fears over credibility

The attack on Thursday came as Myanmar prepares to hold its general elections on November 8. More than 6,000 candidates from 91 parties are registered to take part in the vote.

As Myanmar continues to move away from military rule, the vote is being regarded as the freest and fairest in decades.

UN special rapporteur for Myanmar, Yanghee Lee, warned on Thursday, however, that there could be turmoil in the Asian country if the landmark elections fail expectations of a credible vote.

Speaking at a news conference, the South Korean university professor and rights advocate said that dozens of candidates have been disqualified because they hold foreign citizenship or their parents have foreign passports.

Hundreds of thousands of people who had cast ballots in previous polls have also reportedly been disenfranchised.

"All of the people of Myanmar are really excited about this. It's really a historic moment," said Lee. "But unfortunately, many will not take part in the election process."

There will also be no vote in the northern states of Shan and Kachin, which border China, due to conflict and recent flooding, which has caused major logistical problems.

Lee said that the presence of international observers would be vital to ensuring that the elections are credible.

ksb/ls (Reuters, AFP, dpa)