Chinese Foreign Ministry spokeswoman Hua Chunying said three bombs landed on Chinese territory Dec. 30 during fighting between Kachin rebels and Myanmar forces.
"The Chinese side demands the Myanmar side immediately take effective measures to prevent similar incidents from happening again," she was quoted by China's official Xinhua news agency as saying.
Last week, U.N. Secretary-General Ban Ki-moon expressed concern about the situation in Myanmar following reports of clashes with Kachin rebels.
Fighting in Kachin erupted in 2011, ending a 17-year truce.
The international community last year commended Myanmar, known formerly as Burma, for a series of political reforms that began with general elections in 2010. Security and human concerns continue to tarnish the government's reputation, however.
Beijing said there was no basis to reports last week stating that fighter jets from Myanmar strayed into Chinese territory. The closest fighter jets from Myanmar are about 3 miles from the border, Xinhua reports.