Egyptian opposition groups have said an agreement between Cairo and Riyadh to redraw the Red Sea maritime border between the two countries, ceding sovereignty over two islands to Saudi Arabia, is unconstitutional.

The agreement, which hands sovereignty of the Tiran and Sanafir islands to the kingdom, was announced in an Egyptian cabinet statement on 9 April, following a five-day state visit to Egypt by Saudi Arabia’s King Salman bin Abdulaziz al-Saud.

The cabinet statement went on to say the agreement “enables both countries to benefit from the exclusive economic zone for each, with whatever resources and treasures they contain”.

Local reports said the decision on the islands had come after 11 rounds of negotiations over more than six years

Egypt’s Prime Minister Sherif Ismail said the agreement would be presented to parliament for ratification.

Ownership of the uninhabited islands, which sit at the entrance to the Gulf of Aqaba, has long been disputed, with both Cairo and Riyadh claiming them, although they were under Egyptian control.

Earlier during King Salman’s visit, Egyptian state television said the two nations had agreed to set up a $16bn investment fund, while on Friday the leaders unveiled plans for a Red Sea bridge connecting the two countries.

Past plans for a Red Sea causeway from Saudi Arabia to Egypt passed across the larger island of Tiran.

More than a dozen other accords, including a memorandum of understanding to set up an industrial zone in Egypt, were also announced.

In 2013, MEED reported plans by Saudi state oil company Saudi Aramco to develop the kingdom’s first offshore oil field in the Red Sea, close to the islands.

The company has not made public estimates of the Red Sea’s potential, but there could be up to 100 billion barrels of oil equivalent under the seabed, equal to a 38 per cent increase on Saudi Arabia’s proven reserves of 267 billion barrels.