Britain and the United States have warned their citizens against traveling to Egypt or visiting certain areas. The two countries said Westerners could remain the target of Islamic insurgents.

"American citizens should maintain a heightened awareness of their surroundings and should not linger amid groups of tourists in public areas," the State Department said.

On April 30, an Islamic insurgency cell staged separate attacks near the Egyptian Museum and the Citadel, Middle East Newsline reported. Seven people were injured and the attackers were killed.

On April 7, three Western nationals, including an American, were killed in a suicide bombing. Egyptian authorities have linked the two incidents last month.

"All U.S. citizens are strongly urged to avoid crowded tourist areas in Cairo until the current threat environment diminishes," the State Department said. "Any suspicious behavior should be reported to authorities."

Britain has warned its nationals against traveling to Egypt. The Foreign Office said Britons faced a "continuing threat from terrorism throughout the country."

"A further attack in Cairo cannot be ruled out," the British Foreign Office said in a statement.

The spate of insurgency attacks came amid an increase in protests against the regime of President Hosni Mubarak. On Wednesday, thousands of anti-Mubarak demonstrators clashed with police in several cities in Egypt in unrest led by the opposition Muslim Brotherhood.

The Brotherhood reported demonstrations in Alexandria, Cairo, Damenhour, Fayum, Tanta and Zagazig. About 200 people were said to have been arrested.