Updated

A devastating explosion in northern Iraq was spearheaded by foreign fighters under the sponsorship of Seif al-Islam Gadhafi, son of the Libyan leader, a security chief for Sunni tribesmen who rose up against Al Qaeda in Iraq said Saturday.

Col. Jubair Rashid Naief, who also is a police official in Anbar province, said the Anbar Awakening Council had alerted the U.S. military to the possible arrival in the northern city of Mosul of the Seifaddin Regiment, made up of about 150 foreign and Iraqi fighters, as long as three months ago.

The U.S. military did not immediately respond to an e-mail request for comment about Naief's claim.

"They crossed the Syrian border nearest to Mosul within the last two to three months. Since then, they have taken up positions in the city and begun blowing up cars and launching other terror operations," Naief told The Associated Press.

The so-called Anbar Awakening Council is a grouping of Sunni tribes in the western province that last year turned against Al Qaeda and began working with U.S. forces. The council is credited with the sharp drop in violence in the former insurgent redoubt.

The movement has since been spread by Americans through Baghdad and surrounding districts. That and the introduction of 30,000 additional U.S. troops by mid-2007 are seen as the main factors in the recent decline in violence in the country.

Naief did not explain why the younger Gadhafi would be sponsoring the group of fighters. Seif Gadhafi, however, was quoted by the Austrian Press Agency last year as warning Europeans against more attacks by radical Islamists.

"The only solution to contain radicalism is the rapid departure of Western troops from Iraq as well as Afghanistan, and a solution to the Palestinian question," Gadhafi was quoted as saying.

Touted as a reformer, 36-year-old Gadhafi has increasingly been sharing his father's spotlight and reaching out to the West to soften Libya's image and return it to the international mainstream. He has no official government post, but many see him as the man most likely to take power in the North African country when his father steps down or dies.

The massive explosion in Mosul on Wednesday and the homicide attack assassination of a top police official the next day have prompted obvious concern among Iraq's leaders.

On Friday, the government said it would dispatch several thousand more security forces to Mosul in a "decisive" bid to drive Al Qaeda in Iraq from its last major stronghold.

Prime Minister Nouri al-Maliki gave no details on troop strength or timing, but his announcement added to growing signs that Mosul could represent a pivotal showdown with insurgents chased north by U.S.-led offensives.

"Today, our troops started moving toward Mosul ... and the fight there will be decisive," al-Maliki said during a speech in the Shiite holy city of Karbala.

The challenge, however, is whether the Iraqi forces have the firepower and training to lead an offensive into Iraq's third-largest city. The U.S. military is relatively thin across northern Iraq and has signaled no immediate plans to shift troops from key zones in and around Baghdad.

Mosul is now considered the main logistical hub for Al Qaeda in Iraq because of its size and location — sitting at crossroads between Baghdad, Syria, Turkey and Iran. Many extremists fled north as U.S.-led forces began gaining ground in former insurgent strongholds last year, aided by Sunni tribes that rose up against Al Qaeda and its backers.

Interior Ministry spokesman Maj. Gen. Abdul-Karim Khalaf told The Associated Press that 3,000 police were being sent to the Mosul region to augment the understaffed force.

Ninevah province, whose capital is Mosul, has about 18,000 policemen. But only about 3,000 of those operate in the city of nearly 2 million, according to police spokesman Saeed al-Jubouri.

A Defense Ministry official said several thousand Iraqi soldiers would be moved from Baghdad and Anbar province. He spoke on condition of anonymity because the information is sensitive.

"We have asked the prime minister to send us fresh units because we cannot defeat the terrorists with the weak units we have now in the city," Maj. Gen. Riyad Jalal, a senior Iraqi officer in the Mosul area. "We need new equipment and stronger weapons because most of our security members have only rifles."

Mosul, 225 miles northwest of Baghdad, has become a fulcrum on two fronts.

First the United States is trying to keep Iraqi security forces in the lead as a major test of Washington's long-range plans, which seek to keep a smaller American force in Iraq as backup for local soldiers and police.

Second, U.S. officials say Mosul has become the only remaining major city in Iraq where Al Qaeda is able to operate with any freedom. Major centers of Al Qaeda activity in the past — including the western Anbar province, Baghdad and Baqouba north of the capital — no longer offer easy refuge.

Al-Maliki announced reinforcements for Mosul two days after an abandoned apartment building, believed to be used as a bomb-making factory, was blown apart as the Iraqi army was investigating tips about a weapons cache.

At least 34 people were killed and 224 wounded when the blast tore through surrounding houses in the Zanjili neighborhood, a poverty-ridden district on the west bank of the Tigris River. No soldiers were reported killed.

A homicide bomber then killed a police chief and two other officers Thursday as they toured the devastation. Residents taunted the chief and pelted him with rocks moments before he was killed.