WASHINGTON, March 28 (AFP) - United States President Joe Biden on Sunday (Mar 28) decried the bloodshed unleashed against anti-coup protesters in Myanmar as "absolutely outrageous", after security forces killed more than 100 people including at least seven children.

Myanmar has been in turmoil since the military ousted and detained civilian leader Aung San Suu Kyi on Feb 1, triggering mass protests demanding a return to democracy.

On Saturday, at least 107 people were killed across Myanmar as security forces opened fire on protesters.

"It's terrible," Biden told reporters in brief remarks he gave in his home state of Delaware.

"It's absolutely outrageous, and based on the reporting I've gotten, an awful lot of people have been killed totally unnecessarily."

Saturday's killings came after the junta staged a major show of might for its annual Armed Forces Day.

The European Union described the deadly violence as "unacceptable".

"Far from celebrating, the Myanmar military has made yesterday a day of horror and of shame," EU foreign policy chief Josep Borrell said in a statement.

The condemnation came after the defence chiefs of 12 countries including the US, Britain, Japan and Australia denounced the Myanmar military.

"A professional military follows international standards for conduct and is responsible for protecting - not harming - the people it serves," the rare joint statement said.

"We urge the Myanmar Armed Forces to cease violence and work to restore respect and credibility with the people of Myanmar that it has lost through its actions."

According to a local monitoring group, the death toll from crackdowns since the coup has climbed to at least 423.

Funerals were held on Sunday for some of the victims, after the bloodiest day since the putsch.

In Mandalay, the family of Aye Ko, a father of four, commemorated his life at a service after he was killed overnight.