Bomb kills four soldiers in Egypt's Sinai
The blast, just south of the coastal city of Arish, wounded another 12 soldiers, several of whom were in critical condition.
Egypt has for years been fighting a Sinai-based Islamic insurgency.
The attacks have grown more frequent and deadlier since July 2013, when President Abdel-Fattah al-Sisi, then the defence minister, led the military ouster of Islamist President Mohammed Morsi, Egypt's first freely elected leader.
The insurgency has also spilled over into mainland Egypt, with a series of high-profile assassinations and bombings taking place in Cairo, the capital.
More recently, the militants have targeted Egypt's vital tourism industry, attacking a hotel near the Giza Pyramids and another in the Red Sea resort city of Hurghada.
No one was harmed in the first attack but three tourists, two Austrians and a Swede, were wounded in the second.
A local Islamic State affiliate claimed responsibility for the October 31 crash of a Russian airliner over Sinai, which killed all 224 people on board.
Moscow said the plane was downed by an explosive device smuggled on board.
The crash dealt a major blow to tourism, prompting Russia to cancel all flights to Egypt and Britain to suspend flights to the Red Sea resort of Sharm el-Sheikh, from where the Russian aircraft had taken off.
There was no immediate claim of responsibility for Wednesday's attack.