An Egyptian labour ministry official and three trade union activists were kidnapped in the Sinai Tuesday, the ministry said, and police were investigating whether militants were behind the abduction.
In Cairo, assailants threw a bomb and opened fire on a small traffic police station without causing casualties, security officials said.
It was the latest in a string of militant attacks on security forces following the overthrow of Islamist president Mohamed Morsi in July.
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Much of the violence has taken place in Sinai, where the officials were abducted while en route to a conference in the southern resort town of Sharm El-Sheikh.
Police found their abandoned car near the resort, labour ministry spokesman Alaa el-Din Mohamed told AFP.
An interior ministry official said police were investigating the kidnappings.
Militants have killed scores of soldiers and police in north Sinai since Morsi's overthrow, but have also attacked police in the resort-rich south of the peninsula and elsewhere.
Bedouin tribesman not affiliated with militant groups have also on occasion staged kidnappings in the south, often to force the release of jailed relatives.