Islamic State militants have ambushed a police convoy in Egypt's Sinai Peninsula, killing 18 police and wounding seven others.
It is one of the deadliest attacks this year in the restive region bordering Israel and the Gaza Strip.
Roadside bombs destroyed and set ablaze four armoured vehicles and a fifth one carrying signal-jamming equipment, police and military officials said.
The gunmen later opened fire with machine guns and commandeered a police pick-up truck.
Among those killed were two police lieutenants. The wounded included a police brigadier general.
IS claimed responsibility for the attack in a brief item carried by its Aamaq news agency.
The attack took place about 30 kilometres (nearly 19 miles) west of el-Arish in northern Sinai, the epicentre of a long-running insurgency now led by an IS affiliate.
Monday's attack was the deadliest against security forces since July, when IS militants attacked a remote army outpost in the border town of Rafah, killing 23 soldiers.
That was the deadliest attack in two years.
In March, the military said militants killed 10 soldiers during an army raid in Sinai's central region.
Egypt has battled militants in Sinai for years but the insurgency became far more deadly after the 2013 military ousting of Mohammed Morsi, an elected Islamist president.
In recent years there has also been a wave of attacks, mainly targeting security forces, blamed on splinter factions of Mr Morsi's Muslim Brotherhood group.
Monday's attack came a day after authorities said they had busted a militant cell planning attacks in Cairo.
Police said they killed 10 militants in two simultaneous raids on apartments in a densely populated Cairo neighbourhood.
They said the militants sneaked into the capital from northern Sinai, but did not say whether they were members of IS.
