Kachin rebels and other ethnic groups are battling for more self-rule. Myanmar's President Thein Sein has tried to broker peace agreements with ethnic rebels but talks with the Kachin group have so far failed.
Clashes in Kachin state, in northern Myanmar, broke out in June for the first time since a peace deal was brokered in 1994.
Nearly a dozen clashes between Kachin rebels and government forces have erupted since the end of April, The Guardian newspaper in London reports, citing Myanmar's state-run media.
At least 31 people were killed during the latest clashes, with rebels suffering the greatest loss. The British government was among those who've eased sanctions on Myanmar for its move toward democracy.
The government in 2010 freed pro-democracy leader Aung San Suu Kyi from a lengthy house arrest, weeks before the first general election in years.
British Foreign Minister William Hague this week praised Myanmar for its political reform after Suu Kyi was sworn in as a member of Myanmar's Parliament.
"A number of concerns remain, in particular the need to address the abuse of human rights, a significant number of political prisoners and the continuing conflict in Kachin state," he said in a statement.