The protests began April 26 in opposition to President Pierre Nkurunziza's decision to seek a third term -- something the protesters say is prohibited by the country's constitution, agreed to at the end of a deadly civil war.
Nkurunziza's supporters contend that because he was elected to his first term by Parliament rather than in a popular vote, the limit does not yet apply to him.
Reports said that protesters, after taking a break over the weekend, resumed their demonstrations Monday in Bujumbura, the capital, and that police responded with fire.
"The police have been using live ammunition for several days," Carina Tertsakian, a senior researcher on Burundi for Human Rights Watch, told CNN. Authorities have used tear gas and water cannons as well, she said.
"The situation is really tense," she said. "It seems to be getting more and more tense. The President is not backing down. And the protesters seem to be just carrying on with their protests."
Burundians are leaving their homes and fleeing the violence.
The U.N. high commissioner for refugees said a week ago that "nearly 21,000 Burundians, mostly women and children have fled to Rwanda saying that they have experienced intimidation and threats of violence linked to the upcoming elections."
And the fear, Tertsakian said, is that the flow of refugees will increase.
Burundi is a small country -- smaller than Maryland -- just south of Rwanda, which experienced a horrific explosion of ethnic killing in 1994 in which perhaps 800,000 Tutsis and moderate Hutus were slaughtered in 100 days.
The makeup of Burundi's population of 10.4 million people is similar to that of Rwanda -- the majority is Hutu and a minority is Tutsi. An ethnic civil war in Burundi between 1993 and 2005 killed an estimated 300,000 people.
Upon its end, Nkurunziza became President.
Current tension not based on ethnic identity
Tertsakian, the Human Rights Watch researcher, said the current dispute is not ethnically based. The President and the main opposition group are both Hutu. And the country has made progress in healing its ethnic division, she said.
Nevertheless, she said nonethnic political violence in Burundi in the past has been brutal. And ethnic tension always lurks in the background, she said.
The situation has alarmed the international community.
"Violent suppression of dissent and intimidation of citizens who have a right to protest peacefully is unacceptable in a nation that wishes to strengthen its democratic transition from a post-conflict society," the U.S. Embassy in Bujumbura said in a statement April 26.
The statement went on to deplore the authorities' decision to shut down African Public Radio, the main independent radio station in the country.
"The United States will continue to closely monitor events in Burundi and will take targeted measures, where appropriate, to hold accountable those responsible for violence against the civilian population," the statement said. "We call for the government to begin an open dialogue with the opposition, media and civil society to avert further violence and ensure peace and stability."
The United Nations and the European Union have also expressed concern about the deteriorating situation in the country.
People inside and outside the country have taken to social media to express their views. One hashtag on Twitter is #StopNkurunziza. Some Twitter reports said there were injuries Monday among the protesters, but these accounts could not be verified.
Tertsakian said there have been several deaths among the protesters over the last week and between 300 and 400 people have been arrested.
The President's main opponent in the election is former rebel leader Agathon Rwasa. The vote is scheduled for June 26