A small bomb exploded outside the Israeli embassy in New Delhi on Friday as it marked the anniversary of setting up diplomatic relations with India.
No injuries were reported but an Israeli official told AFP the incident was being treated as terrorism.
The windows on three nearby cars were blown out by what police called "a very low intensity improvised device".
"Initial impressions suggest a mischievous attempt to create a sensation," a police statement added.
However an Israeli official in Jerusalem, speaking on condition of anonymity, told AFP: "We consider this as a terror attack."
With the Indian capital already on heightened alert because of farmers' protests, the district around the embassy was sealed off and flooded with police, paramilitaries, bomb disposal experts and anti-terrorism specialists.
The embassy is on a tree-lined avenue opposite a French cultural institute with other embassies and international schools nearby. All stepped up security.
- 'Flower pot' bomb -
According to media reports, the device, which went off at about 5.05pm (1135 GMT), could have been left in a flower pot or a bottle on the pavement close to the embassy.
India's foreign minister Subrahmanyam Jaishankar said he had spoken to his Israeli counterpart Gabi Ashkenazi about the bomb.
"We take this very seriously," Jaishankar said on Twitter, adding that he had promised "the fullest protection for the embassy and Israeli diplomats."
The "matter is under investigation and no effort will be spared to find the culprits."
Ashkenazi said Jaishankar had promised that India "will continue to act resolutely to locate all those involved in the explosion."
Top security officials from the two countries also discussed the bomb.
The Israeli foreign ministry confirmed there were no casualties and no damage to the embassy. Ashkenazi had asked for "all necessary security measures" to be taken, said a statement.
The incident came on the 29th anniversary of the establishment of diplomatic relations between the two countries -- the Israeli embassy had tweeted about the "birthday" during the day.
The countries have become close allies, and India is now one of the biggest buyers of Israeli defence equipment.
India's Prime Minister Narendra Modi visited Israel in 2017, and his Israeli counterpart Benjamin Netanyahu made a high-profile return visit a year later.
In February 2012 a bomb attack on an Israeli diplomatic car in Delhi injured the defence attache, her driver and two other people. Another attack targeted an Israeli diplomatic car in Georgia the same day, and Netanyahu blamed Iran for both.
Friday's incident took place close to where Modi and other government and military leaders were attending an army parade.
Delhi has been on major alert this week after farmers' protests against government agriculture reforms deteriorated into serious unrest on Tuesday.