A powerful bomb placed in a briefcase outside the High Court in New Delhi killed at least nine people and wounded 45 on Wednesday, the deadliest attack in India in almost two months, prompting the government to put the capital on high alert.

Home Secretary RK Singh, the top interior ministry official, told CNN-IBN television the explosives were placed at a High Court security gate in central New Delhi which scores of people must clear to be able to enter the court.

No one has claimed responsibility for the attack, less than two months after triple bomb attacks in India's financial hub Mumbai killed 24 people.

There is still no word on who was behind those attacks, although police have focused their investigation on the the Indian Mujahideen, a home-grown militant group know for its city-to-city bombing campaigns using small explosive devices.

'The blast occurred at counter number 3 near gate number 5. I was near the gate at that time. There was an orderly queue when a loud blast occurred. I saw many injured and dead. I saw 20-25 injured and around 10 dead,' said lawyer KK Gautam.

'I saw some dead bodies and some dismembered body parts.'

The colonial-style court building is in a leafy, usually tranquil part of New Delhi. Lawyers in black suits and starched white collars stood around shocked on a day when the court hears public interest petitions.

About 120 soldiers, police and bomb squad specialists were at the scene, with ambulances whisking the injured away to hospitals.

'There was panic everywhere. Now we are on the way to the hospital,' witness Kriti Uppal told CNN-IBN. 'It seems to be very powerful (blast). Seems to be many casualties.'

Television images showed scores of lawyers running from one of the main gates of the building just after the explosion. Police cordoned off the area, not far from parliament and the prime minister's office.

'This appears to be a bomb explosion and it is at least a medium-intensity bomb... The site has been fully secured and Delhi has been put on high alert. Whatever precautions need to be taken are being taken,' said UK Bansal, in charge of internal security at the home ministry.

The blast in the heart of the capital will renew concern about the authorities' ability to prevent attacks, particularly in sensitive, high-risk areas.

The blast outside the court, seen as a high profile but soft target, comes at a time when the judiciary is in sharp focus for nudging the government to act on issues ranging from corruption to the environment.

Ruling Congress party politicians have over the past year attacked the Supreme Court for overstepping its authority and intervening in executive functions. The Supreme Court is the highest court in India.

The High Court is the court of appeal at state or provincial level.  "So an attack on such a target will bring you the maximum mileage," said independent strategic analyst Major General Ashok Mehta.

"Also, notice that this comes just days before 9/11, so the government should have expected something like this." 

Several bomb attacks in large Indian cities in recent years have been tied to the Indian Mujahideen, said to have support from Pakistan-based militants fighting Indian rule in Kashmir.-Reuters