Myanmar was described as "like a battlefield" after police today used force to suppress demonstrations, killing at least 18 people.

Police have used real bullets, stun grenades and tear gas on protesters in several cities and towns in Myanmar.

In Yangon, a woman died after police used stun grenades to disperse teachers' protests, but the cause of the death is unknown, Reuters reported.

"The police approached and their guns were ready. We didn't think they were going to shoot for real," Ye Swan Htet, 23-year-old victim's nephew, told the Guardian.

"Myanmar is like a battlefield," Charles Maung Bo, the country's first Catholic cardinal, wrote on Twitter.

Real ammunition was used in many places in Yangon, including Hledan Junction, a gathering point for protesters, after police attempted to disperse the crowd with tear gas and stun grenades.

Many protesters wore masks, covered their noses, wore hats and goggles to protect themselves from the increasingly violent reactions from the police yesterday.

"They shoot civilians ... This is a real crime," said a medical officer who transferred the injured to Yangon General Hospital.

The protests against the military junta and requests for a restoration of democracy in Myanmar are into the fourth week, with the level of violence in clashes constantly escalating.

State Counselor Suu Kyi and many Myanmar civilian government officials were arrested by the military on February 1 in a quick coup.

The US, UK and several countries and organizations called for Suu Kyi's release, and at the same time imposed sanctions against the Myanmar military government and their business partners.