Cairo Egyptian security forces Saturday barred a convoy of humanitarian aid from reaching the Palestinian Gaza Strip citing security reasons, activists said.

The convoy of around 600 political activists, were stopped at a security checkpoint in North Sinai, around 150 kilometres from the Egyptian crossing of Rafah on the border with Gaza.

The activists, who included ex-presidential contender Khaled Ali and prominent politician Jamila Ismail, were to deliver three trucks full of food and medical assistance to residents of Gaza, the target of a 12-day-old Israeli offensive.

Army officers at the checkpoint said safety of the participants could not be ensured in the restive Sinai or inside Gaza and asked them to return to Cairo, according to activists.

“We are on our way back to Cairo along with the aid,” said Tamer Abu Arab, a participant in the convoy. “We have not only experienced trouble, but we are sorry for the people (Gazans), who badly need these supplies,” he wrote on his Facebook account.

The organizers are expected to hold a press conference after their return to Cairo on details of blocking their convoy.

Hamas, who rules Gaza, this week rejected an Egyptian proposal for a truce in the impoverished Palestinian enclave. The proposal, accepted by Israel, calls for an immediate ceasefire between Israel and Palestinian factions, easing a blockade of Gaza and starting separate talks in Cairo between both sides for a comprehensive ceasefire agreement. Gaza, home to around 1.8 million people, has been subjected to an inexorable Israeli siege since 2006.

Egyptian-Hamas relations have been frayed since July last year when the army toppled Mohammad Mursi of the Muslim Brotherhood of which Hamas is an offshoot. Egyptian media has repeatedly accused Hamas of involvement in deadly attacks that have since targeted Egyptian security forces. The Palestinian group has denied the charges.