A U.S. soldier walks towards the site of a suicide attack in the heart of Kabul, Afghanistan.

An explosion rocked central Kabul early on Tuesday and a thick plume of black smoke could be seen rising from the vicinity of the sprawling U.S. embassy in the Afghan capital, Reuters witnesses said, but there was no immediate report of casualties.

Warning sirens blared out from the embassy compound, which is also close to the headquarters of the main NATO-led mission in Afghanistan. There was no indication of the source of the blast, but rocket attacks remain relatively common in the city.

The U.S. embassy said they were not affected by the blast.

The NATO military coalition also said they were unaffected.

Related articles across the web

• Afghanistan: Explosion heard in Kabul
• Bicycle bomb in Kabul embassy district wounds one
• Kabul bomb near US Embassy injures one
• Taliban Assassinate Afghan Army General
• Bicycle bomb in Kabul embassy district wounds one
• Suicide attack leaves at least 26 dead outside Baghdad
• Bicycle bomb in Kabul embassy district wounds guard
• At least 26 killed in suicide attack outside Baghdad
• Are We Going Back To Afghanistan?
• Hard-Line Militant Group Wants 'Power-Sharing' With Kabul In Exchange For Peace