An explosion rocked Kabul on Tuesday morning hours before a major international conference is slated to be held in the Afghan capital.
Witnesses in northern outskirts of Kabul said they heard the explosion, but Afghan security officials were not available for comment.
At least four explosions were also heard near city's international airport on Monday night, but there were not reports of casualties.
Taliban spokesman Zabiullah Mujahid, who was speaking from an undisclosed location, said that their fighters had fired four rockets at the airport. He said the power of the airport was cut as the rockets triggered "heavy explosions".
He could not say if there had been any casualties.
Nearly 70 international representatives are to participate in the Kabul Conference, which will endorse new development projects and transfer more aid money and responsibility to the Afghan administration.
The delegates include representatives from 57 countries and 11 regional and international organisations.
Most of the nearly 40 foreign ministers, including US Secretary of state, Ms Hillary Rodham Clinton, arrived in Kabul on Monday. President, Mr Hamid Karzai, already met several of the foreign dignitaries, his office said.
Security was tightened around the capital city on Monday following a Taliban suicide attack on Sunday that killed three civilians and injured 45 others.
Several roads, including the one linking the city's international airport to the conference venue remained closed for traffic. The government also declared on Monday and Tuesday public holidays in Kabul.
Thousands of security personnel have been deployed around the city, while Nato said t was ready to help with protection if asked. Nato helicopters were also on patrol.
The delegates are to deliberate and endorse 15 socio-economic development national priority programmes drawn up by the Afghan government, while they are also expected to endorse a peace plan by the Afghan government to reintegrate Taliban fighters into civilian life.