AP file photo A Pakistan army officer guards captured Central Asians Abdul Qahar, 26, left, Mohammad Khalid, 16, and Hussain, 14, in Peshawar in 2004. Foreign fighters cross into Afghanistan from Pakistan, terror experts say.

PESHAWAR, Pakistan — Afghanistan has been drawing a fresh influx of jihadi fighters from Turkey, Central Asia, Chechnya and the Middle East, one more sign that al-Qaida is regrouping on what is fast becoming the most active front of the war on terror groups.

More foreigners are infiltrating Afghanistan because of a recruitment drive by al-Qaida as well as a burgeoning insurgency that has made movement easier across the border from Pakistan, U.S. officials, militants and experts say. For the past two months, Afghanistan has overtaken Iraq in deaths of U.S. and allied troops, and nine American soldiers were killed at a remote base in Kunar province Sunday in the deadliest attack in years.

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, warned during a visit to Kabul this month about an increase in foreign fighters crossing into Afghanistan from Pakistan, where a new government is trying to negotiate with militants.

Two U.S. officials, who spoke on condition of anonymity, said the U.S. is closely monitoring the flow of foreign fighters into Afghanistan and Pakistan.

Jihadist Web sites from Chechnya to Turkey to the Arab world featured recruitment ads as early as 2007 calling on the "Lions of Islam" to fight in Afghanistan, said Brian Glyn Williams, associate professor of Islamic history at the University of Massachusetts. Williams has tracked the movement of jihadis for the U.S. military's Combating Terrorism Center at West Point.

Local Afghans in the border regions are increasingly concerned about the return of the "Araban" or "Ikhwanis," as Arab fighters are known in the Pashtun language, Williams wrote in a CTC paper. He said there were rumors of hardened Arab fighters from Iraq training Afghan Pashtuns in the previously taboo tactic of suicide bombing.

Turkey also appears to have emerged as a source of recruits. Williams estimated that as many as 100 Turks had made their way to Pakistan to join the fight in Afghanistan.

"The story of Turkish involvement in transnational jihadism is one of the best kept stories of the war on terror," said Williams, who noted that al-Qaida videos posted on YouTube mention Turks engaging in the insurgency. "The local Afghans whom I talked to claim that the Turks and other foreigners are more prone to suicidal assaults than the local Taliban."

Dozens of Turkish Islamic militants have trained in al-Qaida camps in Afghanistan and taken part in attacks there, said Emin Demirel, an anti-terrorism expert in Turkey. He said images of attacks on mosques or Muslim villages provide propaganda for recruiting young Turkish Muslims.

"Nowadays, they are effectively using the Internet to communicate with fellow militants, and police have difficulty in keeping tabs on several of the jihadist sites," said Demirel, author of several books on Turkish Islamic militant groups. "Turkish courts sometimes locally block access to one particular site, but it is still accessed outside Turkey. Those Web sites eulogize fallen fighters as martyrs in order to recruit among radical Muslim youths."

One example was Cuneyt Ciftci, the German-born son of Turkish immigrants, who took the Arabic nom de guerre of Saad Abu Furqan. In a video obtained in March, the 28-year-old was shown giving a final hug goodbye to some friends before blowing himself up outside a U.S. military base in eastern Afghanistan.

A Turkish news Web site, Uslanmam, said an Uzbek militant group called Islamic Jihad Union claimed responsibility and eulogized Ciftci as "the brave Turk who has left his luxury life in Germany and came here to go to paradise."

A couple of weeks later, newspapers in Pakistan reported that four Turkish nationals with suspected links to al-Qaida had been arrested by authorities on a bus. They were found with explosives, ammunition and jihadi sites on their laptops.

A senior official in Turkey's Interior Ministry said it has no information to corroborate claims of an increase in the number of Turks fighting in Afghanistan. The official asked not to be identified.

Al-Qaida's recruitment drive stems from a slow and steady resurgence that started in 2002, according to Taliban sources.

"They are awake," said Qari Mohammed Yusuf, who Afghan authorities confirm is a senior Taliban member. "They have people going by different names to other countries. They are coming and going easily. In the last year, they have been organizing more day by day."

Al-Qaida has financed the Taliban in both Pakistan and Afghanistan, Yusuf said. In the chaos created by the Taliban groups, al-Qaida has been able to steadily recruit, re-establish its public relations wing, plot new attacks and re-establish areas of operation on both sides of the border.

Afghan and Western officials say a key route for al-Qaida recruits is from Central Asia into northeastern Kunar and Nuristan provinces, where former U.S. intelligence officials suspect Osama bin Laden is hiding.