A massive cyber attack has crippled Internet services in Myanmar ahead of Sunday's election, IT experts and web service providers say, raising fears of a communications blackout for the vote.

Internet users in the military-ruled country have reported slow connections and sporadic outages for more than a week, and some suspect the junta may be intentionally disrupting services to block news flowing out.

Web service providers have blamed the troubles on outside attacks.

"Our technicians have been trying to prevent cyber attacks from other countries," a technician from Yatanarpon Teleport Co. told AFP on condition of anonymity.

"We still do not know whether access will be good on the election day," he added.

A technician from private web provider RedLink Communications Co. said there was still intermittent loss of Internet connection.

Experts say Myanmar's Internet system has been overwhelmed by a flood of incoming messages known as a Distributed Denial of Service (DDoS) attack.

US-based IT security firm Arbor Networks says the main state-owned Internet provider Myanmar Post and Telecommunications "suffered a large, sustained DDoS attack disrupting most network traffic in and out of the country."

The onslaught was "several hundred times" more than enough to overwhelm the country's terrestrial and satellite links, it estimated.

Some Internet users believe the authorities are intentionally slowing services ahead of Sunday's vote, the first in 20 years in Myanmar, which is also known as Burma.

"Although they said the connection has been attacked, it's hard to believe. I think they have been doing it intentionally for the election day to delay news reaching the international community," said Kyaw Kyaw, a 25-year-old university student in the main city Yangon.

The polls have been widely criticised by pro-democracy activists and Western governments as being aimed simply at prolonging military rule under a civilian guise.

Foreign journalists and election monitors are not being allowed into the country for the election.

During monk-led protests in 2007, Myanmar's citizens used the web to leak extensive accounts and video to the outside world, prompting the regime to block Internet access.

Media watchdog Reporters Without Borders describes Myanmar's legislation on Internet use, the Electronic Act, as "one of the most liberticidal laws in the world", with on line dissidents facing lengthy prison terms.