KINSHASA (Reuters) - Supporters of a jailed Christian sect leader on Wednesday attacked the prison in the capital of Democratic Republic of Congo where he was being held, freeing him and about 50 other inmates, the government said.

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A police officer and five attackers were killed in the raid on Kinshasa’s Makala prison, said government spokesman Lambert Mende, who gave no further details.

Ne Muanda Nsemi, a self-styled Congolese prophet and leader of the Bundu dia Kongo movement, was arrested in March after a series of deadly clashes between his supporters and police.

The clashes have compounded tensions since President Joseph Kabila refused to step down when his mandate expired in December and added to fears of instability and civil conflict.

Residents heard gunfire near the prison at around 4 a.m. (0300 GMT) and saw prisoners wearing blue shirts with yellow collars in the streets.

One prisoner, speaking on condition of anonymity, told Reuters more than 4,000 inmates had escaped, roughly half the population. But aside from Nsemi, the most prominent prisoners had not escaped.

These include opposition leaders, war criminals convicted by the International Criminal Court and soldiers convicted in the assassination of former president Laurent Kabila.

The prisoner said the attackers, armed with batons and three AK-47 rifles, easily overpowered the guards who he said had been drinking heavily.

A former prisoner, who said he had spoken to guards and escaped prisoners, also said more than half of the prisoners had escaped.

The United Nations warned its staff to avoid non-essential movement around Kinshasa, saying the situation was calm but unpredictable.

Soldiers stopped young men for questioning near Nsemi’s house in the city’s Ngaliema district and arrested some of them, a Reuters witness said.

The president of Bundu dia Kongo’s political wing could not be reached for comment. A spokesman told the website actualite.cd that the group had no role in the attack and that he did not know Nsemi’s whereabouts.

Nsemi has a strong following in southwestern Congo and wants to revive the Kongo kingdom, which flourished for centuries around the mouth of the Congo River.

At least six of Nsemi’s supporters were killed earlier this year during the two-week standoff at his Kinshasa residence that led to his capture.