Tanzanian President John Magufuli on Sunday ordered an inquiry after police admitted responsibility for the death of a 22-year-old student who was hit by a stray bullet as they sought to break up an opposition rally.
The young woman's death on Friday night triggered an outpouring of national anger and demands for justice.
"I am profoundly shocked by the death of 22-year-old student Akwilina Maftah," Magufuli said in a posting in Swahili on Twitter.
"I have ordered the security forces to carry out an inquiry and to take legal measures against those responsible."
Another four people were seriously injured in the incident as police sought to disperse a peaceful demonstration in Dar es Salaam, the country's commercial capital.
Regional police commander Lazaro Mambosasa said six officers had been arrested for using their weapons during Friday's march as they sought to clear the road of demonstrators from Chadema, the main opposition party.
Police had earlier said the bullet which killed the young woman was one of the warning shots fired by officers during the operation.
Witnesses said police used tear gas and fired live ammunition, while the police accused some of the demonstrators of throwing stones.
- Interior minister under fire -
The shooting triggered a flood of public outrage, with the TNSP, an umbrella group of Tanzanian students, demanding "the immediate resignation" of Interior Minister Mwigulu Nchemba, urging Magufuli to sack him if he refused to go.
The group also said it would help the victim's family to file suit against the police.
The Alliance for Change and Transparency, another opposition party, also called for Nchemba to resign as well as police chief Simon Sirro.
On February 11, Tanzania's Catholic bishops accused Magufuli's government of cracking down on political activities and demonstrations, warning it was creating a political climate which would foment "division and hatred."
Nicknamed the Bulldozer, Magufuli took office in 2015 promising to tackle corruption.
But detractors describe him as autocratic, saying he has clamped down on freedom of expression, with opposition meetings routinely banned and several newspapers shut down.
Several journalists and artists have received death threats for criticising his regime.