KABUL, Afghanistan (CNN) -- An anti-government group led by Afghan warlord Gulbuddin Hekmatyar claimed responsibility for a suicide bomb attack on a convoy of U.S. contractor SUVs near the U.S. Embassy in Kabul Tuesday morning, an Afghan police official said.
Kabul Detective Police Commander Alsiha Paktiwal said two people -- including the bomber -- died and four others were wounded, but private security sources told CNN three people died in the blast.
There were no U.S. casualties, according to the sources, although the identities of the dead were not immediately provided.
The explosion, which could be heard across the city, took place in the Wazir Akhbar Khan neighborhood -- an upscale district of Afghanistan's capital -- about 7:45 a.m. (10:15 p.m. ET).
Hekmatyar's Hezb-i-Islami has claimed responsibility for the bombing, the police chief said.
Hekmatyar is a marginalized Afghan warlord who in July called on all Islamic fighters in Afghanistan -- including the Taliban -- to stop bomb attacks against Afghan civilians and religious leaders.
But there is an indication Hekmatyar, has not completely abandoned his warlord ways -- he signs off with the statement, "Long live the mujahedeens and death to the enemies of Islam."
Hekmatyar's Hezb-e-Islami was one of the groups that helped end the Soviet occupation of Afghanistan in the 1980s. But the group was blamed for widespread violence during that period and many believe that led Afghans to embrace the Taliban.
During his tenure as Afghanistan's prime minister in the early 1990s -- before the Taliban took control -- Hekmatyar enjoyed immense support from neighboring Pakistan. He found himself at odds with Islamabad after it sided with the United States following the September 11, 2001, attacks.
His alliances are unclear. Afghan President Hamid Karzai has tried to include Hekmatyar and other former Afghan warlords in the government, "for the sake of peace in Afghanistan."
But Karzai's cozy relationship with the United States has rankled Hekmatyar and other warlords who are opposed to foreign forces in Afghanistan.
Hekmatyar has also split with many of his Hezb-e-Islami commanders, some of whom plan to form a political party in Afghanistan, a former top mujahedeen commander in Afghanistan recently told CNN. E-mail to a friend
CNN's Nic Robertson contributed to this report.