Twelve people have died during a massive three-day traffic jam in Indonesia that stretched more than 20 kilometres and brought thousands of holiday-makers to a complete standstill, an official said on Friday. The horror traffic at a major highway junction at Brebes, a city on the main island of Java, was so bad that Indonesians dubbed the disastrous toll gate "Brexit", from the words "Brebes exit".

More than 400 motorists had died on Indonesia's roads so far this holiday season, including those in the "Brexit" jam, Pramuraharjo said.

Accidents are not uncommon during the holiday odysseys, particularly on the potholed roads of overcrowded Java, home to more than half of Indonesia's 255 million people.

At the "Brexit" snarl, frustrated motorists posted pictures to social media showing cars snaked back for miles. Aerial shots captured a sea of motionless vehicles, with some drivers seeking respite on the roadside.

Pramuraharjo said roadside vendors and crowded markets near the junction compounded the chaos, leading to traffic snarls "more than 20 kilometres" in length.

"There is a bottleneck there, where there's a petrol station very nearby and many people queue," he said.