Religious extremism could derail the much-vaunted reform process in Myanmar (Burma) , the Buddhist-majority country's first Catholic cardinal, Charles Maung Bo, said on Tuesday.

Bo, who was named a cardinal by Pope Francis on January 4, warned that Buddhist nationalism directed against minority Muslims could drive the latter to connect with international extremist groups that would "retaliate".

"So far they have been more on the quiet side, but if they come with the force of an international community of Muslims, then violence, terrorism, suicide bombers and all these things could happen," Bo told Reuters in an interview at the red-brick cathedral in Yangon, Myanmar's largest city.

Bo called for mutual understanding and urged the government to do more to curb hate speech by radical monks.

Myanmar emerged in 2011 from half a century of military rule, and the semi-civilian government has lifted curbs on freedoms of speech, association and media.

But the reforms have been accompanied by a rise in Buddhist nationalism, with monks forming groups aimed at promoting the country's Buddhist character.

The main target of the Buddhist nationalist movement has been the country's Muslims, who account for about 5 percent of a population of 51 million.

Sectarian violence since June 2012 has killed at least 240 people, mostly Muslims, while almost 140,000 Muslims remain in displacement camps after their homes were destroyed.

Myanmar is also racked by conflicts with ethnic insurgents, who have been battling the government for autonomy, some for six decades. The government is pushing for a national ceasefire pact this year, but the peace process has faltered, with sporadic clashes.

Bo said he was optimistic about Myanmar's reform process, but warned that the military could again seize control if the peace process failed and sectarian violence continued.

"We hope that chaos won't happen," he said, calling on the military to make greater efforts to build trust with ethnic armed groups, and for more monks to speak out against extremism.

"For peace in the country the Buddhist monks also have quite a major role to play too," said Bo, leader of Myanmar's Catholics, who make up about 1.6 percent of the population.

Francis appointed 20 new cardinals, 15 of whom will be eligible to vote for the next pope. It was the first time cardinals from Myanmar, Tonga and Cape Verde were appointed and the appointees from all three nations are electors.