The TNLA and other insurgent groups are fighting with authorities in Myanmar for greater autonomy for ethnic minorities in the area.
A spokesman for the Ta'ang National Liberation Army (TNLA), made up of fighters from the Ta'ang or Palaung ethnic group, admitted it had targeted soldiers and militia who ran the casino on the outskirts of the border town of Muse in northern Shan state.
The fighting erupted at Muse town yesterday in which nineteen people have been killed so far. Mid-day accepts no responsibility or liability for its dependability, trustworthiness, reliability and data of the text.
Of the 18 civilians killed in the attack that began at 5 a.m., 16 were men and two were women, said Zaw Htay. "This is not an ethnic rights movement, this is a terrorist attack".
The UN and human rights groups say the volatile situation in Myanmar is putting people's lives at risk.
He challenged the government statistics about the civilian toll from Saturday's violence, saying it was much lower. "We are sorry. But it's hard to say how they were killed during the fighting", said the TNLAA spokesman.More news: North West politicians pay tribute to Tessa Jowell
Muse in Shan state is situated at a crossing between Myanmar and China's Yunnan province, a major source of trade between the two countries.
It is unclear if members of the powerful Kachin Independence Army, or KIA, took part in the attacks on Saturday though the commander-in-chief's post said they did.
In 2017, Chinese authorities estimated a flare-up of violence to have sent more than 20,000 refugees across the border, and fighting in 2009 and 2015 displaced tens of thousands of people.
The insurgency in the northeast - which is separate from the Rohingya crisis to the west - is one of some two dozen ethnic minority rebellions that have roiled Myanmar's border regions since independence in 1948.
Reverend Hkalam Samsun, chairman of the Kachin Baptist Convention, said the Kachin people were "disappointed" with Suu Kyi.
"She ignored the ethnic issue".