Israeli authorities released a well-known Palestinian rights activist and journalist on Thursday after being held for 18 months under administrative detention, locals told Ma'an.

Nidal Abu Aker, who has served a total of 14 non-consecutive years in Israeli prison, was released to his family in Duheisha refugee camp south of Bethlehem.

Most of Abu Aker's total internment in Israeli prison had been under Israel's policy of administrative detention, or imprisonment without trial or charge.

He was detained on June 28, 2014, after Israeli forces raided his home in the refugee camp and assaulted him and family members.

Abu Aker hosted a radio program called "In their cells" at the Sawt Al-Wehda radio station after establishing the media channel with several friends to promote the issue of Palestinian prisoners.

An administrative detention order was issued on Jan. 15, 2015 for being part of an illegal organization and taking part in illegal activities that constituted a threat to the security of the Israeli state, prisoner rights group Addameer said.

The military order was implemented despite the argument by his defense that he has the right to express his thoughts and opinions as a journalist.

Abu Aker, together with other prisoners, started a hunger strike on Aug. 20 to protest their detention without charge or trial. Around a month later the Israeli Prison Service promised to not renew his detention order.

On Monday, the PA's Committee for Prisoners' Affairs said Israel is now holding some 520 Palestinian prisoners under administrative detention.

The latest number is up from around 370 administrative detainees before a wave of unrest swept the occupied Palestinian territory at the beginning of October.

Administrative detention allows internment without trial for six-month intervals that can be renewed indefinitely.

Israeli officials claim it is an essential tool in preventing attacks and protecting sensitive intelligence because it allows authorities to keep evidence secret.

However, the practice has been strongly criticized by the international community as well as both Israeli and Palestinian rights activists.

They say that international law allows for such detention only under extreme circumstances, but that Israel uses it as a punitive measure on a routine basis to circumvent the justice system or as a crutch to avoid trial.