The Afghan interior ministry and police confirmed there was an explosion in the heavily fortified area but could not immediately provide further details.
It was the first attack targeting the Afghan capital's so-called "Green Zone" since a massive truck bomb ripped through the area on May 31, killing or wounding hundreds. The Islamic State claimed responsibility for the attack. In a tweet, Swaraj said she had a talk with India's Ambassador to Afghanistan Manpreet Vohra after the attack and no Indian nationals were injured.
General Dawlat Waziri, spokesman for the Defense Ministry, said the bomber was on foot. "No casualties to our personnel".
"I was 100 meters away when the explosion happened and as I ran towards the site I saw several people lying in blood - one had been hit in the head and was moving. It was a awful scene", one witness told Afghanistan's Tolo news.More news: Khloe Kardashian calls Tristan Thompson 'daddy' amid pregnancy speculation
Ambulances were seen rushing the injured to nearby hospitals. Gen. Dawlat Waziri said: "At around 4 p.m. a suicide attack took place close to the worldwide affairs office of the Ministry of Defense".
The explosion occurred at 4:06 p.m. local time (1136 GMT) in Wazir Akbar Khan area, a fortified diplomatic enclave in Kabul.
A suicide bomber reportedly detonated his explosives in 14th Street in Wazir Akbar Khan - inside the Green Zone.