Mya Thwate Thwate Khaing's injury also brought scathing global condemnation of the junta. The shootings occurred near the Yadanabon dock, where tear gas and rubber bullets were used on protesters earlier in the day.
But tension escalated quickly in Mandalay where police and soldiers were confronting striking shipyard workers and other protesters.
At least five people were injured by rubber bullets and had to be carried away in ambulances, according to an AP journalist who witnessed the violence.
The first known serious casualty of Myanmar's biggest protests in over a decade had stirred anger across the country, adding to the growing fury over the military's February 1 overthrow of Aung San Suu Kyi's government, three months after her party won a second successive election in a landslide.
Protesters and residents were forced to flee the neighborhood amid the violence, as security forces chased after them.
"We will regard you as our Martyr", wrote one supporter of the protest movement on Twitter.
A young woman protester died on Friday after being shot in the head last week as police dispersed a crowd in the capital, Naypyitaw, the first death among opponents of the coup in the demonstrations.
An impromptu memorial created under an elevated roadway in Yangon attracted around 1,000 protesters.
Mya Thweh Thweh Khine, who recently turned 20, had been in critical condition since February 9, when she was shot at a protest in Naypyidaw.
Her death could become a rallying cry for the protesters who were again on the streets across the country yesterday.
Mya Thwate Thwate Khaing was a teenage grocery store worker in Myanmar's sparse and isolated capital until less than two weeks ago, when a gunshot turned her into a national symbol of resistance. Amnesty said the images were taken from a location near the Thabyegone Roundabout, across the road from where a young woman was shot. "The funeral will be held on Sunday".
"We reiterate our calls on the Burmese military to refrain from violence against peaceful protesters", spokesman Ned Price told reporters on Friday.
Across the country, protests showed no signs of slowing down despite recent crackdowns by the military government - including a sixth consecutive night in which the internet was cut for many hours.
"The UK condemns the military coup and the arbitrary detention of Aung San Suu Kyi and other political figures", Raab said. "We are calling on the armed forces to release detainees and solve democratic problems".
Myanmar has experienced insurgencies by ethnic minority factions since shortly after its independence from Britain in 1948 and the army has long proclaimed itself the only institution capable of preserving national unity.
The junta seized power after detaining Ms. Suu Kyi and preventing Parliament from convening, saying elections in November were tainted by voting irregularities.
The military allege the NLD's landslide election win a year ago was fraudulent but have not provided proof. Demonstrators are sceptical of the army's promise to hold a new election and hand power to the victor.
The U.S., British and Canadian governments have imposed sanctions on the new military leaders, and they and other nations have called for Ms. Suu Kyi's administration to be restored. They have also called for the scrapping of a 2008 constitution that has assured the army a major role in politics since almost 50 years of direct military rule ended in 2011.