KINSHASA (Reuters) – At least one person was killed and an estimated 20 inmates escaped in a prison break in Democratic Republic of Congo’s eastern city of Bukavu on Friday, the mayor said.

The break is at least the sixth in Congo since May and underscores how insecurity has grown since President Joseph Kabila refused to step down at the end of his mandate last December.

The inmates escaped after an unidentified person threw a grenade inside the prison, Mayor Philemon Yogolelo told Reuters.

“The guards are right now counting the prisoners to know if the number of fugitives needs to be adjusted,” Yogolelo said. The prison population is ordinarily around 1,000.

A visitor to the prison was killed and four others wounded when prison guards opened fire, he added.

About 4,000 inmates escaped the capital Kinshasa’s main high-security prison in May after an attack the government blamed on a separatist sect. Another 930 broke out of a prison in the northeastern city of Beni the following month.

The deteriorating security situation, including an insurrection in central Congo that has killed more than 3,000 people since last August, has led some of Kabila’s allies to call on him to decree a state of emergency.

Kabila has ruled Congo, a tinderbox of rivalries over mineral rights and ethnicity, since 2001 and his refusal to quit power has raised fears the country could slip back to the civil wars of the turn of the century that killed millions.