CAIRO (Reuters) - Egyptian security forces killed 10 militants in an exchange of fire and arrested 400 suspects, including foreigners, in a continuing crackdown in Sinai, the army said in a statement carried by state TV on Tuesday.

Based on army statements, around 38 militants have been killed since the latest offensive to crush insurgents blamed for a string of attacks began.

Egypt launched a major security operation on Friday involving the army and police against “terrorist and criminal elements and organisations” across the country, according to the army spokesman.

President Abdel Fattah al-Sisi, who is seeking re-election in March, ordered the armed forces in November to defeat militants within three months after an attack on a mosque killed more than 300 people, the deadliest such violence in the Arab world’s most populous country.

The insurgency poses the greatest challenge to the government in a country that is both the most populous in the Arab World and a main regional ally of the United States.

Sisi was elected for his first term in 2014 after the army ousted Islamist President Mohamed Mursi following mass protests against his rule.