Thousands of people have fled their homes in recent weeks
Burundi's security forces have detained illegally about 200 people suspected of helping the country's last active rebel group, a human rights group says.
The detainees included Senator Benoit Ntaganzwa and his wife, the Burundian Association for the Protection of Human Rights and Detainees said.
They are accused of giving sanctuary to the FNL-Palipehutu rebels.
The army has stepped up operations against the rebels in recent weeks after a rebel assault on the capital.
Earlier Burundi's army says it killed 50 rebel fighters in the latest clashes near Bujumbura.
It was the heaviest fighting since fighting resumed last month.
The association said it did not believe the detainees had committed any crimes and called for the detainees to be released.
"It would be better for the government to release them and continue dialogue in order to finish the war," Jean Baptiste Sahokwsana, spokesman for the Burundian Association for the Protection of Human Rights and Detainees, told the BBC.
"Our people are very tired of this war," he added.
An FNL spokesman has said the rebels would go back to the capital next week to discuss reviving a ceasefire agreement signed more than a year ago.
Peace deals have been signed with most of Burundi's rebel groups - including one which now forms the government - except the FNL.
The BBC's Prime Ndikumagenge in Bujumbura says a ceasefire was agreed with the FNL in September 2006 but it has not been implemented.
Ex-rebel Pierre Nkurunziza was elected president in 2005 under a deal to end years of conflict between the Tutsi army and Hutu rebels.
More than 300,000 people died in the war sparked in 1993 by the assassination of Burundi's first Hutu head of state and democratically elected president, Melchior Ndadaye.