China has threatened to take "decisive" measures if there is a repeat of a deadly attack by Myanmar forces on its territory, allegations that officials in Yangon deny.
Speaking at his annual news conference on Sunday, Li Keqiang, the Chinese premier said that the government had the ability and responsibility to "firmly defend" the stability of the border.
In a similar statement issued late on Saturday, Fan Changlong, who is a deputy head of the powerful Central Military Commission, said Myanmar air force aircraft had crossed the border "many times" recently.
"The Myanmar side must recognise the seriousness of the issue, seriously deal with this incident, punish those who caused the trouble, apologise and pay compensation to family members, and explain themselves to China," Fan was cited as telling Myanmar's military in an emergency telephone call.
Myanmar must take strict steps to rein in its armed forces to ensure no repeat of such incidents, he said.
"Otherwise, China's military will take resolute and decisive measures to protect the lives, property and security of China's people," Fan said, without elaborating.
In an interview with Al Jazeera's Florence Looi on Sunday, Zaw Htay, director of the Myanmar president's office in the capital Naypyidaw, denied that the bomb that killed the farmers came from Myanmar's military.
He also said that GPS data, flight and ground records show that Myanmar's fighter jets did not stray into Chinese territory.
He said Myanmar will cooperate with China, and exchange information with Beijing regarding the incident. But he did not say if Myanmar will launch a formal investigation.
On Saturday, Myanmar's foreign and defence ministers met China's ambassador to Myanmar and Chinese defence attaché in Naypyidaw to discuss the incident.
The incident has tested generally good ties between Beijing and Naypyidaw, that have been strained in recent years by Myanmar's perceived shift toward the United States.
Tension at the border
The farmers' deaths Friday occurred as the Myanmar government stepped up its fight against ethnic Chinese rebels in the country's Kokang region along China's southwestern border.
Beijing strongly protested the bombing and said it had sent fighter jets to warn off further intrusion.
It also summoned Myanmar's ambassador to complain about the bombing.
Tens of thousands of people, many of them ethnic Chinese, have fled the fighting in northeastern Myanmar's Kokang region into China.
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 China's Yunnan province.
China and Myanmar share a 2,000km border, much of it remote and hard to access.