Mads Gilbert, a Norwegian doctor who is an outspoken critic of the Israeli military’s campaign in the Gaza Strip, has been permanently banned from entering the Palestinian enclave by Israeli authorities, according to media reports. Gilbert, who has reportedly treated patients in Gaza for over a decade, was also present in the region during the recently concluded 50-day war.

Gilbert reportedly said that in October, when he was attempting to return to Gaza through the Israeli-controlled Erez crossing, he was denied entry by the military, which cited “security reasons” for the decision.

The 67-year-old doctor, who has done extensive volunteer work in hospitals across the Gaza Strip, suggested that his vocal criticism of Israel’s occupation of Palestinian territories could be the reason for his indefinite ban, according to media reports.

Gilbert, who has reportedly described Israel’s actions in Gaza as “state terrorism at the highest level” was also one of the co-signatories in a strongly-worded letter denouncing Israel, published in July in medical journal The Lancet.  

“The truth on the ground is very inconvenient for Israel. Anyone who conveys that truth is unwanted,” he reportedly said. “This is not about me. This is about Israel denying the Palestinian people in Gaza international support… To deny professionals from the medical field the right to go to Gaza is another aspect of the collective punishment.”

A senior Israeli government official, however, said that the denial of entry was related to “security issues” and had nothing to do with Gilbert’s “anti-Israeli and anti-Semitic remarks,” according to media reports.

Gilbert also said that he would continue to call for the “long overdue” siege of Gaza to be lifted, according to an Al Jazeera report.

“The Israeli authorities are, in my opinion, in no position to deny the Palestinian people support from the international community,” he reportedly said. “I will not give up travelling to Gaza as long as they have medical needs.”

The Norwegian government said that it would challenge the ban, according to media reports.