American troops in Iraq have discovered a series of underground bunkers used by insurgents, the US military says.
The US military says it has found dozens of caches in Anbar province
A spokesman said the complex in an abandoned quarry in the restive province of Anbar covered an area the size of four football pitches.
The bunkers are said to contain a large stockpile of weapons and living areas with air conditioning and showers.
Meanwhile, Iraqi authorities said they had arrested an insurgency leader and key al-Qaeda figure in Mosul.
The arms cache was one of 50 found in recent days in Anbar province, west of Baghdad, the spokesman said.
Tips from locals and information from detainees had helped to identify the locations uncovered in the ongoing operation, the spokesman said.
He said nobody was in the underground complex near the town of Karma when it was found.
Inside they discovered weapons, ammunition, black uniforms and ski masks, night vision goggles and fully-charged mobile phones.
The complex also contained four furnished living spaces and a kitchen with fresh food, the spokesman said.
US and Iraqi forces continue to battle insurgents in the vast province following a major assault on rebels in Falluja last November.
Also on Sunday, the Iraqi government announced the arrest of Mutlaq Mahmoud Mutlaq Abdullah, also known as Abu Raad, in the northern city of Mosul.
The government said he was a facilitator and financer for Abu Talha, the alleged leader of al-Qaeda's operation in Mosul, and therefore closely linked to Iraq's most wanted militant, Abu Musab al-Zarqawi.
It was the second major arrest announced in Mosul in two days.
On Saturday, police said they had captured Mahdi Moussa al-Jabouri, also known as Mullah Mahdi, who allegedly headed the Mosul cell of the radical Islamist group Ansar al-Sunna.
The group has been blamed for many deadly attacks in Iraq, including a suicide attack on a US military base near Mosul in December that left 22 people dead.
A defence ministry spokesman said Mullah Mahdi was "one of the most dangerous terrorists in the country".