Human Rights Watch is urging Burma to drop charges against activists who led protests to mark the United Nations' International Peace Day without government permission.

The New York-based group said Tuesday that up to 13 activists face possible charges for organizing last month's peaceful demonstrations, which called for an end to violence against ethnic minority groups. Authorities rejected the application to hold the protest, saying it would disrupt traffic, pose a threat to the public and could result in violence.

Two protest leaders have already been charged with organizing the unauthorized protest. The government has threatened charges against 11 others. The peace activists could face up to 10 years in prison, if they are charged separately in each of the 10 townships they passed through without receiving permission.

Phil Robertson, Human Rights Watch's deputy Asia director, says the charges seem aimed at intimidating others from holding anti-government protests. He says the nominally civilian government will “quickly lose its reformist label if it is . . . arresting and prosecuting peaceful protesters.”

The global rights watchdog says the case represents a test for Burma's reformist government and its 2011 public assembly law, which requires all protests to receive government permission. Other rights groups have also criticized the law, saying it is too vague and could be used by authorities to stifle dissent.