May 25 (Bloomberg) -- About 1,000 U.S. Marines, sailors and members of Iraq's security forces encircled the western Iraqi city of Haditha today in the second offensive against insurgents in the region this month, the U.S. military said.

Six insurgents were killed and two Marines were wounded in a gun battle at 4 a.m. local time, the military said. Residents identified one of the attackers as an imam, the U.S. said.

The action is aimed at ``maintaining the pressure on insurgents that began with Operation Matador,'' in which 125 militants were killed and 39 arrested, the military said in e- mailed statements. Nine U.S. Marines died and 40 others were wounded in the May 7-14 offensive, the military said.

Today's operation, dubbed New Market or Suq Jadeed in Arabic, follows the announcement yesterday on an Islamist Web site in the name of al-Qaeda in Iraq that the group's leader, Abu Musab al- Zarqawi, was wounded. The U.S. military said May 5 that tribes in Haditha were sheltering al-Zarqawi. The U.S. is offering $25 million for information leading to his arrest.

Militants have killed almost 700 people in Iraq since the government of Prime Minister Ibrahim al-Jaafari was announced April 28. The government says many of the insurgents are non- Iraqis who have entered western al-Anbar province from Syria, which shares a 380-mile (611-kilometer) border with Iraq.

Imam's AK-47

The attacker identified as an imam by locals in today's gun battle opened fire on the Marines and Iraqi Security Forces with an AK-47 Assault rifle, the military said. Checkpoints have been set up around Haditha to prevent insurgents from leaving the city, according to the statement.

One weapons cache consisting of a rocket-propelled grenade launcher, a machine gun and ammunition was discovered buried in a palm grove north of Haditha, the military said, adding that neither Marines nor Iraqi Forces have entered or damaged any mosques in the course of the operation.

The 3rd Battalion of the 25th Marines has been conducting operations in and around Haditha for three months to root out militants, the military said. Insurgent activity has recently increased in the area, the U.S. said, citing the discovery of numerous roadside bombs and indirect fire attacks launched against coalition forces assigned to protect Haditha.

Operation Matador, which focused on the town of al-Qaim, near the border with Syria and 186 miles west of Baghdad, also involved a U.S.-led force of more than 1,000. The raid was spurred by information collected from Iraqis living in the area and captured aides of al-Zarqawi, the military said.

To contact the reporter on this story: Caroline Alexander in London at calexander1@bloomberg.net

Last Updated: May 25, 2005 09:50 EDT