Clashes have erupted in the Egyptian capital Cairo during protests against the government’s handover of two islands to Saudi Arabia.

Police fired tear gas and birdshots at stone-throwing protesters as hundreds defied a government ban and gathered in Mesaha square of Cairo on Monday to protest the government’s decision earlier this month to give control over Tiran and Sanafir, two strategic Red Sea islands, to Saudi Arabia.

Eyewitnesses said protesters pelted a police van with stones while others chanted slogans against President Abdel Fattah el-Sisi who has defended his move on the islands, warning that his government would not tolerate demonstrations over the issue.

Sisi and his interior minister warned Sunday that security forces would deal firmly with protesters.

Thousands of police and soldiers were deployed Monday across Cairo ahead of planned demonstrations while many of the protest organizers' gathering points were sealed off.

Reports have indicated that dozens of activists and journalists have been arrested in recent days. On Monday, police briefly detained a group of journalists. Police also blocked entries to doctors' and journalists' unions in central Cairo, stopping and searching pedestrians near those places.

Social media users said heavy police presence and fear of arrest prevented protesters from even gathering, forcing them to form small groups in the hope of assembling elsewhere.

The protesters planned the demonstrations for Monday to coincide with the Sinai Liberation Day, a national holiday marking the completion of Israel's withdrawal from the peninsula in 1982.

The action is the second this month against the decision to give up control of the islands at the mouth of the Gulf of Aqaba. More than 2,000 people protested against the move in downtown Cairo on April 15, the biggest public demonstration since Sisi took office in 2014.