REUTERS - Dutch authorities are investigating death threats against a Palestinian rights activist in The Hague targeted because she has made submissions to the International Criminal Court's inquiry into the 2014 Gaza conflict.

Nada Kiswanson, a legal researcher at Palestinian rights group Al-Haq, said the threats began early this year and have continued on a regular basis since.

"My channels of communication have been totally compromised," Kiswanson told Reuters, adding that she had received death threats by e-mail, via family members and in the form of flower deliveries to her home with accompanying messages.

When she purchased an anonymous pre-paid mobile phone number, she received a threat on it a day later. Messages had come in Dutch, English and "broken Arabic", she said.

The Jordanian-Swedish citizen had also been called on a family member's pre-paid Jordanian number while staying in the country, while a relative in Sweden had been called and told that Kiswanson would be "eliminated."

Human rights organization Amnesty International said it was forced to temporarily close its office in The Hague for security reasons after an employee's personal e-mail was hacked and used to send Kiswanson a death threat.

Since the start of 2015, the ICC has been conducting a preliminary examination of possible crimes committed by both sides in the Gaza conflict, in which more than 2,000 died. Israel, which rejects the court's authority, put its dead at 67 soldiers and six civilians.

Dutch authorities confirmed they were investigating threats against Kiswanson, first reported publicly by newspaper NRC Handelsblad, and that they had put in place measures to protect her.

Although the war crimes court's cases are always highly contentious, rights workers have never before been threatened in the Netherlands.

The court's handful of prosecutors and investigators are heavily reliant on the work of human rights organizations and volunteers to provide background information on the war crimes and crimes against humanity it investigates around the world.

Actual investigations must be carried out by prosecution staff.

Court officials have not yet been able to send a mission to Gaza. Kiswanson submitted information to prosecutors that was collected by Al-Haq at the time of the conflict.

Activists and witnesses linked to ICC cases have been threatened in the past. Judges at the court have said threats against witnesses contributed to the collapse of the crimes against humanity case against Kenyan President Uhuru Kenyatta last year.