The killing by Myanmar’s military of more than 100 pro-democracy protesters in the single deadliest day since February’s coup has drawn outrage from across the world, and calls for a stronger global response.

The US secretary of state, Antony Blinken, strongly condemned the junta, saying Washington was “horrified” by the deaths on Saturday, and that the violence shows “that the junta will sacrifice the lives of the people to serve the few”.

“I send my deepest condolences to the victims’ families. The courageous people of Burma reject the military’s reign of terror,” he said.

The killings on Saturday – Myanmar’s annual Armed Forces Day, which commemorates the start of resistance to Japanese occupation in 1945 – would take the number of civilians reported killed since the coup to more than 440.

UN special rapporteur Tom Andrews said it was time for the world to take action – if not through the UN Security Council then through an international emergency summit. He said the junta should be cut off from funding, such as oil and gas revenues, and from access to weapons.

“Words of condemnation or concern are frankly ringing hollow to the people of Myanmar while the military junta commits mass murder against them,” he said in a statement.

“The people of Myanmar need the world’s support. Words are not enough. It is past time for robust, coordinated action.”

The criticism came as top military officials from the US and its allies prepared to issue a statement condemning Myanmar’s security forces, saying the country’s military has lost credibility with its people.

“As chiefs of defense, we condemn the use of lethal force against unarmed people by the Myanmar armed forces and associated security services,” the draft statement read.

It was signed by 12 chiefs of defence from Australia, Canada, Denmark, Germany, Greece, Italy, Japan, Netherlands, New Zealand, South Korea, UK and the US.

The EU delegation to Myanmar described Saturday as a “day of terror and dishonour”. Dominic Raab, the UK foreign secretary, said the country had marked a “new low”. “We will work with our international partners to end this senseless violence, hold those responsible to account, and secure a path back to democracy,” he said.

The US ambassador, Thomas Vajda, strongly condemned Saturday’s violence. “On Myanmar’s Armed Forces Day, security forces are murdering unarmed civilians, including children, the very people they swore to protect,” he said. “This bloodshed is horrifying. These are not the actions of a professional military or police force.”

The joint statement by military chiefs, obtained by Reuters ahead of its planned release this weekend, is a rare declaration by the most senior military commanders from countries around the world, including in Asia and Europe.

News reports and witnesses said Myanmar security forces killed 114 people, including some children, on Armed Forces Day – the bloodiest day of its crackdown on pro-democracy protesters since last month’s military coup.

Myanmar’s military has so far ignored criticism of its violent crackdown on dissent.

Myanmar’s military has said it took power because November elections won by Aung San Suu Kyi’s party were fraudulent, an assertion dismissed by the country’s election commission and international observers. Aung San Suu Kyi remains in detention at an undisclosed location and many other figures in her National League for Democracy party are also in custody.

While the draft statement by foreign military chiefs did not explicitly condemn the 1 February coup, which ousted Aung San Suu Kyi’s elected government, it said that a professional military must follow international standards for conduct “and is responsible for protecting – not harming – the people it serves”.

It said the country’s military must “cease violence and work to restore respect and credibility with the people of Myanmar that it has lost through its actions”.

The London-based Burma Human Rights Network reacted to Saturday’s violence by calling on the international community to tighten economic sanctions on Myanmar’s business interests and impose a global arms embargo and a no-fly zone in the country’s ethnic conflict zones.

“Every day the horror committed of the Burmese army gets worse as they become more desperate to cling to the power they stole from the people,” the network’s executive director, Kyaw Win, said. “The international community must respond immediately to end this nightmare for the Burmese people.”

New US and European sanctions this week increased external pressure on the junta, but Myanmar’s generals have enjoyed some support from Russia and China, both veto-holding members of the UN security council that could block any potential UN action.

Russia’s deputy defence minister Alexander Fomin attended a parade in Myanmar’s capital Naypyitaw on Saturday, having met senior junta leaders a day earlier.

Diplomats said eight countries – Russia, China, India, Pakistan, Bangladesh, Vietnam, Laos and Thailand – sent representatives to the Armed Forces Day parade, but Russia was the only one to send a minister.

Amnesty International called for a stronger international response, including a UN arms embargo and sanctions on the top generals, although Russia and China’s veto power in the Security Council makes it unlikely any such measures could be passed.

“This is just the latest example of the military authorities’ determination to kill their way out of nationwide resistance to the coup,” said Ming Yu Hah, Amnesty International’s deputy regional director for campaigns.

“These abhorrent killings again show the generals’ brazen disregard for the inadequate pressure applied so far by the international community. The cost of international inaction is being counted in bodies.”

The Guardian