Palestinian activist Muna El Kurd was released late on Sunday after being arrested in an Israeli police raid, her father told The National.
Her twin brother Mohammed was also released after turning himself in to the authorities.
Ms El Kurd, 23, pioneered the Save Sheikh Jarrah campaign for the neighbourhood at the centre of a long-running legal battle and high tensions in occupied East Jerusalem.
"They shut down Sheikh Jarrah neighbourhood for three weeks. Why? Because our voices reached the world," she said after her release.
Ms El Kurd told reporters that her release was "without conditions," before adding that she was prevented from contacting her brother inside the facility where she was held.
"We are free and unafraid. They cannot intimidate us," Mohammed El Kurd wrote on Twitter after his release.
"Their crime was to raise their voices about the plight of Sheikh Jarrah," her father Nabil El Kurd told The National by phone, referring to his children.
“Our heads, and the heads of all of Jerusalem’s youth are held high above the occupation and all their laws. They have not been able to intimidate or terrorise us. We beat them using social media - and the media they control.”
Mohammed El Kurd was released on a 5000 shekel bail, on the condition he must respond to the authorities if he is again called in for questioning.
Stun grenades could be heard exploding in the background as Israeli security forces continued to disperse a press conference held by Mr El Kurd outside the detention centre where the two activists were being held.
A video posted online earlier on Sunday showed Israeli police raiding the El Kurd family’s home. A source close to the family said it took place at 10am that day.
In the video, Ms El Kurd is seen putting on a headscarf before being taken away in handcuffs by police.
Her brother was not home at the time but was asked to report to authorities for "questioning", their father told Palestinian news service Wafa.
The two siblings have featured prominently on social media and in news coverage of an ongoing court case over the right to live in the tiny East Jerusalem neighbourhood.
Social media users rallied behind the El Kurds using hashtags such as #FreeMonaElkurd and its Arabic equivalents, which were shared thousands of times on Twitter alone.
At the press conference late on Sunday afternoon, a committee for the Sheikh Jarrah community called the arrests an "act of terror by the Israeli occupation to impose their authority over Jerusalem".
"We condemn the practices of the Israeli occupation against residents and journalists of the neighbourhood of the occupied Jerusalem," members of the committee said.
On Saturday, Israeli forces detained and released Al Jazeera journalist Givara Budeiri, who was covering events in Sheikh Jarrah.
The Doha-based outlet said Ms Budeiri was "assaulted" in police custody and her cameraman, Nabil Mazzawi, had his equipment destroyed.
Israeli settler groups claim ownership of the homes of around 12 families in the area.
In October, an Israeli court ruled in favour of Jewish settlers who say that several Palestinian families in Sheikh Jarrah are living on land owned by Jews. Jordan – which controlled the area at the time – and the UN settled the families there after they were displaced from their homes elsewhere in the creation of Israel.
The families have appealed the October verdict and are awaiting a delayed decision by the Supreme Court. The evictions are on hold until then.
The situation in Sheikh Jarrah was one of the triggers of the 11 days of fighting between Israel and Hamas in the Gaza Strip.
An Israeli police spokeswoman told Reuters "police arrested, under court order, a suspect, 23, who is a resident of East Jerusalem, on suspicion of participating in riots that took place in Sheikh Jarrah recently".