"This is a government that is effectively saying the only choice is to either murder African migrants on the borders of Israel or send them back to torture and murder in their countries," said Hossam Bahgat, head of the Egyptian Initiative for Personal Rights.
"Our biggest fear is this is going to expand to include all African migrants," he added.
Activists say the Eritreans may have been targeted because of their rising numbers. Anat Ben Dor, head of the refugee rights law clinic at Israel's Tel Aviv University, says Eritreans recently surpassed Sudanese as the largest group of African migrants in Israel. Nearly all come via Egypt.
The Eritreans include Pentecostal Christians fleeing religious persecution who activists say may be drawn to Israel for religious reasons, and others trying to avoid military service. Many are not keen to stay in Egypt, where they face racism and economic marginalisation, rights activists say.
The United Nations, which says Eritrean deportees risk torture in Asmara, has appealed to Egypt for information on the location and fate of 1,400 detained Eritreans, although rights groups say most of them have likely already been deported.
WELCOME WEARS THIN
Egypt, facing international pressure over the deportations, agreed last week to let the UN refugee agency visit detained Eritreans for the first time since February, when it cut access. Teams saw 140 Eritreans but were denied access to hundreds more.
Egypt's foreign ministry has criticised the "Western wail" over the migrants and says Cairo was simply trying to balance its security needs with respect for international obligations.
But there have long been hints that Egypt's welcome of African migrants was wearing out. Police killed over two dozen Sudanese in 2005 when they broke up a sit-in near UN offices in Cairo by asylum seekers demanding resettlement in the West.
But activists say despite its crackdown, Egypt is unlikely to see a huge drop in African migrants trying to pass through, noting a muted global reaction to the recent deportations.
Eritreans in particular have already taken significant risks to leave their country, and do not see other nearby states such as Sudan or Libya as safe or attractive options, activists said.
"They are already risking getting shot on the border to get into Sudan," said Bill Van Esveld, a fellow at Human Rights Watch. "I don't think this is going to stop them from coming...There is nowhere else for them to go."
