U.S. and Iraqi forces searching Iraq's western province of Anbar on Saturday uncovered a network of bunkers hidden in a vast underground quarry and equipped with air conditioning, food and a wide assortment of weapons, a Marine spokesman said.

The quarry, near the town of Karmah, was as long as three football fields and had been divided into rooms that apparently had housed insurgents, the spokesman, Capt. Jeffrey S. Pool, said in a statement.

"Within the various rooms making up the facility, Iraqi security and coalition forces discovered four fully furnished living spaces, a kitchen with fresh food, two shower facilities and a working air conditioner," Pool said.

The weapons stored in the facility included mortars, artillery shells and rockets, according to Pool, who said night-vision goggles and cell phones were also found.

Over three days, Pool said, combined American and Iraqi forces assigned to the 2nd Marine Division discovered about 50 caches of arms and ammunition in Anbar.

The restive province has long been a stronghold of the Iraqi insurgency and a conduit for foreign guerrillas heading for the heart of the country. One month ago, the Marines mounted a seven-day assault in far western Anbar aimed at wiping out foreign insurgents there and their means of support.

In neighboring Nineveh province, local authorities, tribal leaders, police and U.S. military officials met and negotiated an agreement designed to halt a spate of fighting in the town of Tall Afar.

The scene of frequent clashes between insurgents and U.S. forces in the past two years, Tall Afar has recently been rocked by conflict between its Sunni Muslim and Shiite Muslim inhabitants. Sectarian strife has increased in Iraq since a Shiite-led government was installed at the end of April.

Nineveh's deputy governor, Khisro Goran, said after the negotiations that the assembled groups publicly acknowledged the presence of insurgents in the town and agreed that Shiites and Sunnis should not fight over religion. If the pact is not honored, Goran said, the only recourse would be a major incursion by security forces.

Meanwhile, the violence that has claimed more than 800 lives in little more than a month subsided Saturday.

In Mosul, 220 miles north of Baghdad, U.S. and Iraqi forces captured a man whom Iraqi officials called one of the top insurgent leaders in northern Iraq. An afternoon raid in Mosul's eastern industrial sector netted Mullah Mahdi, also known as the Prince of Princes, along with five other suspected insurgents and some car bombs, according to Maj. Gen. Khalil Ahmed Obeidi of the Iraqi army.

"Mulla Mahdi is an Iraqi who belonged to the Ansar al-Sunna group," Obeidi said, referring to one of Iraq's most active insurgent organizations. Obeidi added: "We surrounded the area, and then they surrendered to us. No clashes took place."

In Irbil, a city in the Kurdish-populated northeast, the regional assembly elected in January held its first session.

Kamal Karkukly, who was elected deputy speaker of the assembly, called the session a "step to unify the Kurdistan people and reinforce its stands on federalism." Kurds battled the government of Saddam Hussein to gain independence, but since Hussein's overthrow two years ago many Kurdish leaders have supported their region remaining part of Iraq if a suitable federal system can be forged.

Special correspondents Dhlovan Brwari in Mosul and Marwan Ani in Irbil contributed to this report.

An Iraqi soldier inspects car registration papers at a Baghdad checkpoint.