At least six people were killed as Myanmar security forces fired on pro-democracy protesters Wednesday, after the junta hit half a dozen detained journalists, including an Associated Press photographer, with criminal charges.

The country has been in chaos since February 1 when the military launched a coup and detained civilian leader Aung San Suu Kyi, ending Myanmar's decade-long experiment with democracy and sparking daily mass protests.

International pressure is mounting -- Western powers have repeatedly hit the generals with sanctions -- and Britain has called for a United Nations Security Council meeting on Friday.

But the junta has ignored the global condemnation, responding to the uprising with escalating force, and security forces used lethal force on demonstrators again on Wednesday.  

Four people were shot dead during a protest in a city in central Myanmar, according to medics who spoke to AFP by phone. 

Another two demonstrators died about two hours' drive away in Mandalay, the nation's second biggest city, medics told AFP. 

One of the victims in Mandalay was shot in the head and the other in the chest, according to a doctor, who asked not to be named. 

A protest in the central city of Myingyan also turned violent, as security forces confronted protesters in hard hats crouching behind red home-made shields emblazoned with the three-finger salute -- a symbol of resistance for the anti-coup movement.

"They fired tear gas, rubber bullets, and live rounds," a volunteer medic on the scene told AFP, adding that at least 10 people were injured.

Demonstrations also continued across Yangon, Myanmar's largest city, on Wednesday, with protesters using makeshift tyre and barbed wire barricades to block major roads and slow the police. 

In downtown Pansodan Road, near the famed Sule pagoda intersection, protesters pasted print-outs of junta leader Min Aung Hlaing's face on the ground -- a tactic aimed at slowing down security forces who will avoid standing on the portraits.

In another San Chaung township, which has been the site of intense clashes in recent days, tear gas and fire extinguisher clouds filled the streets as riot police confronted protesters.

Sunday was the bloodiest day since the military takeover, with the UN saying at least 18 protesters were killed across the country. 

Wednesday's violence came after the foreign ministers of Southeast Asian nations -- including Myanmar's junta representative Wunna Maung Lwin -- discussed the crisis at a virtual meeting.

After the talks Indonesia's Foreign Minister Retno LP Marsudi expressed frustration over the junta's lack of cooperation.

Singapore -- which is Myanmar's largest investor -- condemned the authorities' use of lethal force, with Premier Lee Hsien Loong telling the BBC that it was "unacceptable"