Mads Gilbert, an outspoken Norwegian doctor and activist who treated patients at Gaza’s al-Shifa hospital during Israel’s assault on the Palestinian territory this summer, has been denied access to Gaza "indefinitely" by Israeli authorities.

Gilbert told Al Jazeera on Friday that he was turned away from the Erez border crossing when attempting to return to Gaza in October, despite having all the legitimate paper work.

"To my surprise I was denied access by the Israeli military," he said. "When I asked the reason they informed me that it was a security issue."

Gilbert said that when he asked for a fuller explanation, he was told to "leave the premises or the police would be called".

Telling the world about the burdens of the Palestinians in Gaza is considered a security risk. Mads Gilbert, Norwegian doctor

The 67-year-old, who has been involved in solidarity work with Palestinians for decades and volunteered at al-Shifa on and off for 17 years, has been a vocal critic of Israel's military campaigns and its occupation of Palestinian territory.

During the seven-week conflict between Israel and the Hamas movement that left more than 2,000 Palestinians dead, Gilbert frequently spoke to international media, including Al Jazeera, about the situation at al-Shifa hospital, which was overwhelmed with civilian casualties.

However, a spokesperson for the Coordination of the Government Activities in the Territories, the Israeli authority that coordinates all traffic between Gaza and Israel, told Norwegian newspaper Verdens Gang that the refusal of entry was related to security reasons and had "nothing to do with Gilbert's anti-Israeli and anti-Semitic remarks".

Norwegian pressure

Gilbert told Al Jazeera he was informed that the ban was "infinite without any time limit".

He said he had been invited by the Gaza Health Ministry, which had requested his assistance to research the impact on healthcare of the Israeli bombardment and to follow up on work done during that time.

The Norwegian embassy in Tel Aviv has made numerous inquiries to the Israeli government about the ban.

Bard Glad Pedersen, state secretary at the Norwegian Foreign Ministry, told Verdens Gang, "we have raised Gilbert's exclusion from Gaza and asked Israel to change their decision. The humanitarian situation in Gaza is still difficult and there is a need for all health workers."

Medical Aid for Palestinians, a UK-registered charity, which has been working in the occupied West Bank and Gaza for over 20 years and supports al-Shifa hospital, called the ban on Gilbert "deeply concerning" and reiterated that, "following the recent conflict, thousands of Palestinians in Gaza require specialised surgical treatment and it is imperative that the right to health is unimpeded".

'Will not give up'

Denouncing his entry ban as a limitation of freedom of expression, Gilbert said it appeared the Israeli government "doesn't want the effects of their continuous attacks on the civilian population in Gaza to be known to the world".

"Telling the world about the burdens of the Palestinians in Gaza is considered a security risk," he said, adding that in a larger perspective, the ban was not about him, but about the Gazans' right to international assistance.

"The Israeli authorities are, in my opinion, in no position to deny the Palestinian people support from the international community," he told Al Jazeera.

He vowed to continue to challenge Israel and called for political pressure to be exerted to lift the "long overdue" siege of Gaza.

"There is no way we’re going to accept that medical and humanitarian assistance to the people in Gaza shall be denied just because the Israeli government has decided so. I will not give up travelling to Gaza as long as they have medical needs," he said.

Israel launched "Operation Protective Edge" following firing of rockets by Palestinian armed groups from Gaza.

According to UN figures the Palestinian death toll was 2,131, of whom 1,473 were identified as civilians, including 501 children. On the Israeli side, 77 people, mostly soldiers, were killed.