The target was a concert held by an ethnic minority group in conflict with the ruling military, opposition groups and media reported.
An air strike killed at least 50 people at a concert in Myanmar held by an ethnic minority group in conflict with the ruling military, opposition groups and media said on Monday.
The jet strike late on Sunday in the northern state of Kachin, which the military has yet to confirm, killed civilians, local singers and officers of the Kachin Independence Army (KIA), media reported, citing witnesses who said three planes carried out the attack.
While BBC Burmese has put the death toll at no less than 50 people, news site Irrawaddy's estimate was of around 100.
The attack has been condemned by the United Nations and western embassies, with the UN in Myanmar stating that it was "deeply concerned and saddened" by the reports and offering its condolences to the families of those affected.
"What would appear to be excessive and disproportionate use of force by security forces against unarmed civilians is unacceptable and those responsible must be held to account," it said in a press release.
KIA spokesperson Naw Bu said the attack targeted celebrations of the 62nd anniversary of the founding of the Kachin army's political wing, the Kachin Independence Organisation (KIO).
"This is quite a wicked act that can be also considered war crimes," he stated.
Myanmar has been afflicted by open conflict since the army overthrew an elected government early last year. Resistance movements, some armed, have emerged across the country, which the military has fought with lethal force.
Since the coup, fighting has resumed between the Myanmar army and the KIA, which has been fighting on and off for six decades to obtain greater autonomy for the Kachin people. The KIA has voiced support for the anti-junta resistance.
A spokesperson for the junta could not immediately be reached for comment on the airstrike and state television made no mention of the incident in its nightly news bulletin on Monday.