The Burmese government has signed a ceasefire agreement with a prominent ethnic rebel group, in what appeared to be a major breakthrough in efforts to end a 63-year insurgency.

Government officials signed the deal Thursday with the Karen National Union during a meeting in Pa-an, the capital of Karen state.

Karen rebels, which operate in southeast Burma, have been fighting government forces for autonomy since just after the country gained independence from Britain in 1948.

While members of the KNU said the development was positive, they warned that a single meeting cannot end decades of fighting.

The group says the government's anti-insurgency campaigns have subjected them to human rights abuses, including forced labor, looting, extortion and destruction of their property. Thousands of villagers have been forced to flee to escape the fighting.

One-third of Burma's population is made up of various ethnic minorities, and its former military government justified its crackdown on rebel groups as a way of maintaining stability and unity.

Since coming to power in March, the nominally civilian government of President Thein Sein has made a series of reforms, including resuming dialogue with opposition and rebel groups.

In December, the Burmese government signed a preliminary ceasefire with the Shan State Army. It has also reached ceasefire deals with several other ethnic groups, but tensions remain with various other factions.

The government last year revealed a new peace offer to rebel groups that calls for a ceasefire followed by development assistance and then a national conference to discuss political grievances. It was the first time the government had offered to hold political discussions with the rebels.

The United States and other Western nations have demanded Burma arrive at peace agreements with its ethnic rebel groups in exchange for ending economic sanctions.