BEIJING: China has made a diplomatic complaint to Myanmar after three bombs landed on its territory during air attacks on ethnic minority rebels in Kachin state, just over their shared border, Beijing said Friday.

"The Chinese side has launched representations with the Myanmar side requiring them to take effective and immediate measures to avoid the repetition of similar incidents," foreign ministry spokeswoman Hua Chunying said.

The bombs landed just inside China on Sunday evening and caused no casualties, she told reporters at a regular media briefing.

Fighting between the Myanmar military and the Kachin Independence Army in the far north of the country, which is also known as Burma, has worsened in recent days as government forces battled to regain one of their bases.

Tens of thousands of people have been displaced in Kachin state since June 2011, when a 17-year ceasefire between the government and the Kachin Independence Army, the armed wing of the Kachin Independence Organisation, broke down.

Hua refused to be drawn on whether China would mediate between the two sides in an effort to end a conflict which has overshadowed wider political reforms in the country.

"The issue concerning northern Myanmar is Myanmar's internal affair and we hope that the Myanmar government can appropriately deal with the issue through peaceful negotiation," the spokeswoman said.