Protesters say they are angry over a lack of services and delayed salaries, urging the UN to pressure the government into implementing economic reforms.
The Saudi-led coalition said the Houthi group had launched the objects at civilian targets in Saudi Arabia.
A Saudi-led coalition joint force will monitor a ceasefire between separatists, backed by UAE, and the Hadi administration in Abyan province, where fighting has raged over the past six months.
Saudi-backed Yemeni government and the UAE-supported Southern Transition Council have reached a deal to fight against the Houthis.
The deal will reportedly see the secessionist Southern Transitional Council (STC) handed a number of ministries, and the government return to the southern city of Aden, according to officials.
The power-sharing deal would see the secessionist Southern Transitional Council (STC) handed a number of ministries, and the government return to the main southern city of Aden, say officials.
The UAE, which had already in June scaled down its military presence in Yemen, says it will continue fighting "terrorist organisations" in southern provinces and other areas.
A joint statement by the two Gulf states called on the UAE-backed separatists and the Saudi-backed government to prepare for "constructive dialogue" to end the crisis between the two nominal allies.
Houthi and medical officials say the detention centre was holding at least 170 people when it was hit.
Talks between Saudi-backed government and UAE-backed separatist rebels reach a dead-end as both sides gather troops to prepare for further battles deepening rift between Riyadh and its ally Abu Dhabi.
The Saudi-led coalition says it attacked an area in Aden that allegedly poses a "direct threat" to the Saudi-backed government of Abd Rabbu Mansour Hadi. The separatists began withdrawing shortly after.
The coalition late on Saturday threatened military action to halt the fighting and ordered the separatists to withdraw from government military camps they seized in the southern port city.
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