Israel’s military has ordered a Palestinian journalist to be held for four months without charges or trial.

The military said Omar Nazzal is being held in administrative detention on suspicion of “unlawful activity” for the Popular Front for the Liberation of Palestine, a PLO faction that has been labelled a terrorist organisation by Israel.

His lawyer, Mahmoud Hassan, said he believes his client, a leading member of the Palestinian journalists’ union, is being targeted because of his political activism. Hassan noted that under the system of administrative detention, the defence is not shown any alleged evidence against them.

Nazzal, 53, has been in custody since he was seized at an Israeli-run crossing between the West Bank and Jordan last month, while traveling to a meeting of the European Federation of Journalists.

The journalist headed Palestine Today, a TV station affiliated with the militant group Islamic Jihad, for five months, but quit earlier this year shortly before Israel shut the broadcaster down. He also had ties to the PFLP which in the past was involved in attacks on Israelis.

Hassan denied his client was linked to violence, adding: “This arrest is a political arrest.”

Monday’s court announcement comes on the eve of World Press Freedom Day, the lead-up to which Palestinians have been using to condemn Israel.

Hanan Ashrawi, a Palestinian political leader, on Monday urged immediate intervention to ensure Israel was “accountable for the blatant and planned escalation against Palestinian media”.

The journalists’ union says that Israel is also holding in detention another 19 Palestinian journalists and students of journalism, one of them for more than 20 years.

The number of Palestinians in administrative detention reached 627 at the end of February, according to official prison service figures regularly published by the Israeli rights group B’Tselem. Critics say Israel’s large-scale use of the practice amounts to a violation of rules of due process.

The number of administrative detainees has doubled since the start of the latest round of Israeli-Palestinian violence in September. Since the autumn, attacks by Palestinians have claimed the lives of 28 Israelis and two Americans, while about 200 Palestinians have been killed by Israeli security forces.