A huge explosion was heard in Afghanistan's capital early on Tuesday, Reuters news agency reports.
The cause and extent of casualties, if any, were not immediately known.
The blast rattled windows in the heart of Kabul's diplomatic quarter and sirens were soon heard wailing.
The Taliban have claimed responsibility for a suicide car bomber that attacked a foreign motorcade in Kabul, killing at least three international troops and injuring 13 people.
The blast happened just off a busy road that runs from the US Embassy to the airport, near the country's Supreme Court.
The Taliban claimed responsibility for the attack in an emailed statement to journalists. The international military coalition ISAF did not have any immediate information.
The attack comes as the country's two presidential contenders continue negotiations to form some sort of national unity government.
A bomb attack near the US Embassy in the Afghanistan capital Kabul has killed four international troops, an official Coalition statement has said.
At least five were wounded in the blast, which was claimed by the Taliban. Afghan Deputy Interior Minister Mohammad Ayub Salangi earlier said on Twitter a suicide car bomber had targeted a convoy of foreign troops.
A huge blast has been heard in the Afghan capital Kabul. A large plume of smoke could be seen above the city, Reuters reports.
The cause of the explosion was not immediately known and no information on casualties was immediately available.
A fierce gunbattle between Afghan security forces and militants in a building near Kabul airport has now ended, according to reports by AFP.
An attack on Kabul airport has now ended after the gunmen were killed, officials have said.
Gunmen have used rockets to attack Kabul International Airport in the Afghan capital, a senior military official has said.
The gunmen occupied two buildings, which were under construction and used them as a base to fire rockets and gunfire toward planes at the airport, according to NBC News.
ISAF jet fighters are currently flying over Kabul, said Afzal Aman, a general in the Afghan army in Kabul.
An explosion followed by bursts of gunfire have been heard near Kabul International Airport in the Afghan capital.
Smoke was also seen rising above the facility, which is used by civilians and the military, a Reuters witness said.
NBC News Chief Foreign Correspondent Richard Engel, who is in the Afghan capital Kabul, wrote on Twitter: