The group of refugees from Somalia, Eritrea and Ethiopia are now being sheltered in a UNHCR facility in Tripoli until they are evacuated to other countries, he said.
But 654 increasingly desperate people remain in "dire" conditions at Zintan, where the situation is tense, Baloch added.
"All available options must be immediately pursued to release the remaining detainees," he said, urging nations to help evacuate migrants and refugees from the city.
"With no detention centre in Tripoli currently suitable for hosting refugees and migrants, in part due to the ongoing hostilities, UNHCR reiterates its call to the international community to carry out further evacuations of refugees out of the capital," said Baloch.
UNHCR is providing the refugees from Zintan with food, shelter, medical assistance including psycho-social support, as well as clothes, shoes, hygiene kits and blankets, he said.
"Conditions in Zintan are dire," Baloch stated.
The detention centre is severely overcrowded and lacks proper ventilation, while some of its toilets are overflowing and are in urgent need of repair, he said.
"As a result, solid waste and garbage has piled up inside the cell for days and presents a serious health threat," Baloch said.
Meanwhile, a spike in the number of migrants and refugees being returned to Libya by its coastguard means they are being brought to Tripoli's detention centres at a faster rate than people are being evacuated, he noted.
Despite the "extremely volatile" security situation in Libya and a lack of safe ports, a total of 1,224 people were brought back there by Libyan coastguard in May alone - more than in the rest of the year combined, Baloch underlined.
"Renewed efforts are needed to prevent people who are rescued or intercepted in the central Mediterranean from being taken back to Libya," he said.
( With inputs from IANS )