Egyptian troops in Egypt's Sinai Peninsula barred an aid convoy of activists and medical volunteers from reaching the Rafah border crossing with the Gaza Strip on Saturday, as a deadly conflict with Israeli forces intensified.

The convoy, which left Cairo in the early hours of Saturday, was stopped at the North Sinai Balooza checkpoint when forces said that the supplies could pass into the embattled enclave but people would not be allowed to, citing security concerns.

"Despite carrying complete permits, we were blackmailed, [being told] that only supplies, not medical volunteers, could be allowed to move ahead," said Mohamed El-Baqer, of the Popular Committee to Support the Palestinians’ Uprising, at a press conference late on Saturday outside the Journalists Syndicate in downtown Cairo.

The authorities have not issued any statements on the incident.

The convoy of 11 buses and over 550 activists was meant to deliver humanitarian aid to the beleaguered territory, which on Sunday entered the 13th day of an Israeli military onslaught that has left at least 410 Palestinians dead, including many women and children.

During the conference, activists shouted slogans condemning Egyptian President Abdel-Fattah El-Sisi for restrictions imposed by Egypt on the border passage – which has remained mostly closed by authorities, only opened intermittently to receive wounded Palestinians during the recent bout of hostilities between Gaza rulers Hamas and Israel.

"From the first minute, all security and state bodies have been informed of the convoy, its contents and its route," Khaled Ali, former presidential candidate and rights lawyer, told reporters.

He said that the convoy had obtained all necessary permits from the ministries of foreign affairs and health and both general and military intelligence.

Another aid convoy – with the same permits – will head for the Gaza border in the middle of this week, he said.

Political activist Zizo Abdo, who was part of Saturday's convoy, told Ahram Online before the group headed back to Cairo that he and fellow volunteers "tried all kinds of escalation before deciding to go back" but that Egyptian authorities "still refused our entry."

Convoy members initially started to negotiate with army personnel manning the checkpoint and then proceeded to form a sit-in in front of the checkpoint – but to no avail.

The medical assistants accompanying the convoy were also denied entry.

Balooza checkpoint is roughly 200km from the Rafah border crossing and is the entry point to North Sinai, an already troubled area where the Egyptian army is fighting a militant insurgency that spiked following the ouster of president Mohamed Morsi last July.

Students, workers and prominent political figures including Constitution Party member Gameela Ismail and well-known revolutionary icon Ahmed Harara were among the volunteers, according to Abdo.

The Rafah border crossing has mostly remained closed by Egyptian authorities, who cite security concerns related to the rise in Islamist militancy in Sinai.

Convoy members used the hashtag "#Egypt2Gaza" on social media to document their journey.

Similar Egyptian convoys were able to cross into Gaza during the Israeli assault on the strip in 2012, although at the time militant activity in Sinai was vastly reduced and there were no Israeli ground troops in Gaza.

An earlier headline and abstract implied the convoy was halted by the authorities at Rafah; this has been amended.