Heraldo de Madrid - What we know about deadly Delhi car blast

But in the days since Monday's blast, which hospital officials told AFP had killed at least 12 people and wounded 30, authorities have released few details.

Indian media, meanwhile, has been rife with speculation about the most nation's serious security incident since April 22, when 26 mainly Hindu civilians were killed at the tourist site of Pahalgam in Indian-administered Kashmir, sparking clashes with Pakistan.

New Delhi has condemned the November 10 explosion as "a heinous terror incident" carried out by "anti-national forces".

Here is what is known so far:

- What happened? -

The car exploded near a busy metro station close to the historic Red Fort in the capital's Old Delhi quarter -- where the prime minister delivers the annual Independence Day address.

Prime Minister Narendra Modi called the incident a "conspiracy".

However, key facts are unconfirmed.

That includes who was in the vehicle, what type of explosive was used and whether the blast site was the intended target.

It is unclear whether the attack was carried out by a domestic group or had foreign links.

The explosion occurred just hours after police arrested several people, and seized explosive materials as well as assault rifles.

Police said the suspects were linked to Jaish-e-Mohammed (JeM), a Pakistan-based group with Al-Qaeda ties, and Ansar Ghazwat-ul-Hind, a Kashmir offshoot linked to JeM.

Regarding those arrests, India's Jammu and Kashmir police said it was a "white collar terror" group, involving "radicalised professionals and students in contact with foreign handlers, operating from Pakistan and other countries".

But no official has linked the earlier arrests with the Delhi explosion.

- How has India responded? -

The anti-terrorism National Investigation Agency (NIA) is leading the probe.

Police have conducted sweeping raids since the blast, including in disputed Kashmir, targeting the banned Islamist political party, Jamaat-e-Islami (JeI) -- but there has been no confirmation this is connected to Monday's explosion.

Kashmir has been divided between India and Pakistan since their independence from British rule in 1947, and both claim the Himalayan territory in full. Tensions remain high between New Delhi and Islamabad.

Police also arrested several suspects, including doctors affiliated with Al-Falah University in Faridabad, on the southern outskirts of the capital.

Again, officials have not said those detained are connected to the explosion.

- Why is India appearing cautious? -

Home Minister Amit Shah has said the government is awaiting the results of a "swift and thorough inquiry".

Following the April attack in Kashmir, India took one day to say that the gunmen had "cross-border linkages" with Pakistan -- claims Islambad denied.

In May, India conducted strikes inside Pakistan, triggering four days of intense conflict that killed at least 70 people.

After a ceasefire, Modi vowed that "any attack on Indian soil will be considered as an act of war".

Public expectations for a strong response to Monday's blast are therefore extremely high.

Security agencies are under pressure to produce an airtight investigation, given the potential consequences of assigning blame.

But diplomatic considerations may also be shaping New Delhi's stance.

India is keen to secure a major trade deal with the United States, its largest trading partner, after President Donald Trump imposed 50 percent tariffs on Indian goods over its purchases of Russian oil.

Trump has publicly taken credit for brokering the ceasefire between India and Pakistan in May and has cultivated closer ties with Islamabad following its praise of him.

Modi, consistent with New Delhi's longstanding opposition to third-party mediation in Kashmir, said the deal was agreed directly.

B.Roman--HdM