Myanmar expressed "deep sorrow" on Monday for the deaths of five people across the border in China's Yunnan province that it has been blamed for, and said it was jointly investigating the incident with Beijing.
China has said a bomb fell from a Myanmar aircraft on a sugarcane field in Yunnan on Friday, killing four people and wounding nine. One of the injured later died.
On Saturday, a senior officer said China's military would take "decisive" measures if there was a repeat attack by Myanmar forces on its territory. Beijing also summoned the Myanmar ambassador to register a protest.
Myanmar has said the bomb may have been lobbed by rebels it is fighting in the Kokang region bordering China.
"We would like to express our deep sorrow for (the) death and injuries of Chinese nationals living in border areas as a consequence," the government said in a statement published in the state-backed Global New Light of Myanmar newspaper.
It added that the two countries' foreign and defence ministries were in direct contact over an investigation into the incident. "(A) thorough investigation will also be made whether the Kokang insurgent group is involved in this incident to have a negative impact on the friendship between Myanmar and China and to create instability along the border area."
In China, too, efforts were being made to rein in tensions.
The Global Times , an influential tabloid published by the official People's Daily, said in an editorial that the best way for China to ensure stability along its border was to actively push for peace in northern Myanmar.
"If (we) can help Myanmar to effect ethnic reconciliation and lasting peace, that will have the most thorough positive effect. In reality, this ought to be the long-term direction of China's developing diplomatic power."
Myanmar has said Chinese mercenaries were fighting with the rebels, and it has urged China to cooperate to prevent "terrorist attacks" being launched from Chinese territory. China has denied that any attacks into Myanmar have been launched from its territory.
The rebels are from a group called the Myanmar National Democratic Alliance Army (MNDAA), which is led by ethnic Chinese commander Peng Jiasheng. The MNDAA was formed from remnants of the Communist Party of Burma, a powerful China-backed guerrilla force that battled the Myanmar government until it splintered in 1989.
The group struck a truce with the government which lasted until 2009, when government troops took over their region in a conflict that pushed tens of thousands of refugees into Yunnan.
China and Myanmar share a 2,000 km (1,250 mile) border, much of it remote and hard to access.
