(Adds details, background)
CAIRO, Feb 16 (Reuters) - An explosion on a tourist bus in Egypt's Sinai near the Israeli border wounded four people, an army source said.
Israeli police said they heard an explosion from the Egyptian side of the Taba border crossing. The blast took place after the bus entered Egypt from Israel, security sources said.
Egypt has been rocked by political turmoil and violence since the army overthrew president Mohamed Mursi of the Muslim Brotherhood in July after mass protests against his rule.
Islamist militants based in the largely lawless Sinai peninsula near Israel have stepped up attacks on security forces since Mursi's downfall, killing hundreds.
Mursi appeared in court on Sunday on charges of conspiring with foreign groups to commit terrorist acts in Egypt.
(Writing by Michael Georgy; Editing by Janet Lawrence; Editing by Janet Lawrence)