BANGKOK (AFP) - Two eight-year-old girls have been charged under a draconian Thai junta law for tearing down voter lists for an upcoming referendum, police said Saturday (July 23), as authorities go to increasingly bizarre lengths to muzzle dissent.

The junta is determined to see a charter it drafted pass in the Aug 7 poll and has outlawed critical discussion of the document with a 10-year prison sentence.

Campaigning of any kind is also banned and authorities have already arrested or warned scores of people for handing out critical leaflets or wearing "Vote No" t-shirts.

The eight-year-olds fell foul of the law after confessing this week to tearing down voter lists outside a school in northern Thailand because they liked the paper's pink colour.

The pair have been charged with "obstructing the referendum process, destroying official documents and destroying common public property", said Damrong Phetpong, the police commander of northern Kamphaeng Phet province.

They will not face jail time as Thai law exempts anyone under the age of 10 from criminal punishment, he said, adding that police were still duty-bound to file the charges.

"Police have a duty to compile witnesses and evidence and then refer the case to a public prosecutor" who will decide whether to pursue the case, he told AFP.

The junta has become increasingly jittery ahead of the poll, with police initially speculating that anti-junta activists were behind the torn voter lists.

But an investigation led officers to the girls, who were questioned at a police station.

The junta opened monitoring centres across the country this month and is on high alert to block any movement against the charter from supporters of the ousted government, who are expected to vote it down.

This week authorities shut down a critical satellite TV station run by that political bloc, which has seen two of its governments removed by coups in 10 years.

The junta bills its new charter draft as a way out of the political crisis that has bludgeoned the kingdom for the past decade.

But critics and rights groups have lambasted the document and say it will solidify the military's sway in government and diminish the power of elected politicians.