The group also said that Egypt has prevented it and London-based Amnesty International from entering Gaza from its territory since 2012.
On Sunday, Israeli Defense Minister Avigdor Lieberman - who has neither confirmed nor denied Israel's part in the assassination - was quoted by Walla as saying, "Let Hamas look to itself for the culprits".
Hamas, which controls Gaza, has blamed Israel's Mossad intelligence agency for the killing of Mazen Faqha who was found shot dead at his home on 24 March.
The inability to get foreign human rights workers into and out of Gaza, therefore, also limits the ability of human rights groups to document Palestinian abuses inside Gaza, because of safety concerns for local staff.
Aid from the worldwide community remains a lifeline for 1.1 million people in Gaza, and one in four children in Gaza is in need of psychosocial support, she says. Males between the ages of 15 and 45 are being blocked from traveling altogether.
So far, according to the World Health Organisation, 79 Gazan patients have missed medical appointments in Israel because of the restrictions.
Since Hamas took power in the Gaza Strip in 2007, 96 death penalties have been handed down, mostly by military courts and often for spying on behalf of Israel, said Hamdi Shaqura of the Palestinian Center for Human Rights. Until then, the authorities should add human rights workers to those eligible for travel permits. "Freedom of movement is a fundamental human right". Hamas says it wants to stop the killers from fleeing Gaza. It has imposed a gag order barring publication of details into the investigation.
It said in a statement that it allows over 1,000 people to cross through the border each day for a variety of purposes, including business, medical treatment and academic studies, and said all criteria are in line with security needs. It said Kerem Shalom, the main cargo crossing for deliveries into Gaza, has been operating as normal.
In the wake of last month's assassination of a senior Hamas commander in Gaza, the terrorist organization's security apparatus launched a massive campaign to round up and arrest "Israel-collaborators", the Hebrew news site Walla reported.
Faqha, 38, originally from the West Bank, had received nine life sentences for planning a 2002 suicide bombing in Israel in which nine people were killed and 52 were wounded.