A Thai court has jailed seven activists for campaigning against a draft Constitution which is backed by the military. The draft will be put to a referendum in August.

The authorities arrested 13 people while they were handing out leaflets on Thursday motivating people to vote against the charter. "Six have been released but seven will be jailed," Kumklao Songsomboon of the Thai Lawyers for Human Rights group told AFP.

All political parties on both sides of Thailand's divide have joined hands and said the draft constitution is undemocratic. They also said it will preserve the military power and weaken civilian politics.

The government has banned any sort of criticism of the charter in the lead-in to the vote and has already issued notice to stop anyone from campaigning for either side, before the referendum. If anyone violates the rule, he will be jailed for 10 years.

In a statement on Friday, Amnesty International urged the Thailand government to ease the restraint on democratic activities. "These crude tactics represent the latest in series of attempts by the Thai military authorities to muzzle dissent," said Champa Patel, Amnesty International's Senior Research Adviser for South East Asia and the Pacific.

"If a small group of activists cannot hand out leaflets, then what hope is there that the rights to freedoms of expression and assembly will be respected in the run up to the referendum," he asked.