Ramallah, Occupied West Bank- Palestinian leaders in Israel have denounced the arrest of Sheikh Raed Salah, leader of the northern branch of the Islamic Movement, as politically motivated and called for his immediate release.

Salah was arrested at his home in Umm Al Fahm, northern Israel, in the early hours of August 15 on charges of inciting violence and supporting a banned organisation. On Monday, an Israeli court extended his detention until August 24.

"I am sure that this is a political arrest," said Mohammed Barakeh, chairman of the Higher Committee for the Arab citizens of Israel. "This is a kind of anti-democratic act to put the Arab population in Israel under pressure."

The arrest was widely publicised in Israel, and senior figures in the government quickly praised the move. Gilad Erdan, Israeli public security minister, said that Salah encouraged "extremism" and promoted violence and murder. The minister of communication, Ayoub Kara, said that Salah should be deported from Israel.

At a court hearing on August 17, the police presented allegations that Salah gave inflammatory speeches, including one at a funeral for the three Palestinian citizens of Israel who killed two policemen outside al-Aqsa Mosque on July 14.

His detention was extended until August 21, but the judge also stated that some of the quotes cited by the police as evidence of incitement were taken out of context, while some were Quranic verses.

Jamal Zahalka, a Palestinian Knesset member who leads the Balad faction of the Arab Joint List in the Israeli parliament, said that Salah's arrest was part of a wider political trend in Israel targeting Arab political life in the country.

"Its aim is to frighten people from coming to al-Aqsa," Zahalka said. "It's part of the political persecution of our political leaders here inside Israel. It reflects that Israel is strongly shifting to the right and there is a narrowing of political rights and freedom of speech for Palestinian citizens of Israel."

Salah, a former mayor of Umm al Fahm, has been arrested and imprisoned by Israeli authorities several times since he entered public life. He has previously been jailed for fighting against Israeli police officers around al-Aqsa Mosque and was most recently imprisoned for nine months in 2016 on historical incitement charges relating to a sermon he gave in 2007.

The northern branch of the Islamic Movement, which Salah has led since its split from the southern branch in 1996, was declared an illegal organisation by Israel in November 2015. Israel accused the movement of working with the Gaza-based Hamas and leading a campaign of incitement that centred around al-Aqsa Mosque. The charges were denied by Salah and the Israeli decision to ban the movement remains contentious.

"It's a political movement which acts within the framework of nonviolent activity, and they [the Israelis] called it 'terrorist' activity," Zahalka told Al Jazeera.

"We demand the immediate release of Sheikh Raed Salah. We demand that the Islamic Movement have the right to express itself and to implement its political activities as a part of our political map."

FEATURE: Five things you need to know about al-Aqsa

Under Salah's leadership, the northern branch has championed the cause of protecting al-Aqsa Mosque from what Palestinians say is a 'Judaisation' plan by Israel, a charge that the Israeli leadership has denied.

It reflects that Israel is strongly shifting to the right and there is a narrowing of political rights and freedom of speech for Palestinian citizens of Israel. Jamal Zahalka, a Palestinian Knesset member

Al-Aqsa compound is a 35-acre compound referred to as al-Haram al-Sharif, or the Noble Sanctuary, by Muslims, and as Temple Mount by Jews. In recent years, the number of Jews visiting the site around Jewish holidays has risen, while a growing number of right-wing Jewish organisations have sought to increase the Jewish presence at the site and lobbied for Jews to have increased visitation and prayer rights.

Salah has styled the Islamic Movement as a guardian of al-Aqsa and successfully promoted the holy site as a unifying religious and nationalistic symbol for Palestinians in Israel, Jerusalem and across the occupied Palestinian territories.

Its presence has extended through much of the Old City, neighbourhoods in occupied East Jerusalem and beyond, through a network of non-profits and associations involved in welfare and development.

Salah has also proved adept at organising political activism around al-Aqsa, providing buses for worshippers from around Israel to the mosque throughout the year and holding an annual rally attracting thousands under the banner 'al-Aqsa is in danger.'

That sentiment was clearly present among the Palestinian worshippers who joined the massive protests in July after Israel installed metal detectors and security cameras outside the al-Aqsa Mosque in the wake of the July 14 shooting.

"He has managed to present himself as one of the leading personalities around the consolidation of Muslim Palestinians around the holy site," said Eran Tzidkiyahu, a Research Fellow at the Forum for Regional Thinking. "Challenging Israel, challenging certain elements in the Palestinian Authority, the Jordanians, you can see how his influence echoes beyond the site itself, into Israel, into the territories, into Jerusalem and in the regional arena."

"The fact that he [Salah] has been going in and out of custody in the last couple of years, is an indication of how much he threatens the Israeli policy goals, or, stability in the eyes of the Israeli authorities," he added.