Iraq's autonomous Kurdish region is digging a trench along its border with Syria to prevent the infiltration of militants and smuggling from the war-racked country, officials say.

"The trench is designed to prevent the infiltration of members of terrorist groups and stop smugglers," Halkurd Mullah Ali, the spokesman for the Kurdish region's peshmerga security ministry, told AFP.

Smugglers "began operating in these areas because the Syrian authorities lost control of them, and these areas became insecure," Ali said.

The trench is 17 kilometres (10 miles) long, two metres (yards) deep and three metres wide, and is "part of an Iraqi (federal) government strategy" to protecting the country's 600 kilometre border with Syria.

"We arrested terrorists and smugglers trying to infiltrate into Kurdistan," said peshmerga Brigadier General Hashem Yeti, adding that there were "requests from the people of the border areas to prevent the infiltration operations, which represents a threat to them."

But the Democratic Union Party (PYD), a powerful Syrian Kurdish organisation, condemned the trench as an attempt to blockade the country's Kurds, and closed the border crossing with Iraqi Kurdistan in protest.

Hundreds of people have been waiting to cross since the border was closed on Saturday.