Terror seems to have come to a full circle in national capital New Delhi [Images], which was rocked by serial blasts in the busy Sarojini Nagar area of South Delhi three years back.

With Saturday evening's serial blasts in New Delhi, the number of unsolved cases has gone up with police and security agencies groping in the dark about the main perpetrators behind these attacks.

In India, we dont catch terrorists

The serial blasts in the national capital on the eve of Diwali in 2005 that claimed over 60 lives began a fresh chapter of unsolved cases with central security agencies.

Claims by Delhi Police about some arrests in this case came under a cloud as Tariq Dar, arrested in connection with the case, accused the police of framing him. No headway was made.

While there have been claims by police and agencies of busting one module or the other, terrorists seem to have demonstrated that they are very much active and can strike at will, says a senior security official.

Saturday evening's serial blasts that left at least 21 dead, was the fourth near-synchronised explosion this year. Three of such audacious attacks -- Bangalore (July 25), Ahmedabad (July 26) -- have taken place in less than seven weeks claiming 73 lives.

Sarojini Nagar explosion was followed by blasts outside Sankat Mochan Temple in Varanasi in March 2006 followed by the 11/7 serial train blasts in Mumbai that left nearly 200 people dead.

The Anti-Terrorist Squad in Uttar Pradesh [Images] picked up nearly a dozen people from various states in this connection, but the perpetrators and conspirators could not be booked.

The year 2006 wound up with another blast at Malegaon in Maharashtra that left 30 people dead. The police rounded up some locals and filed a chargesheet but the same was put on hold after locals demanded a fresh investigation by the CBI.

CBI was also probing the twin blast case in Hyderabad that took place in August last year, but has failed to achieve any breakthrough.

While Harkat-ul-Jehadi Islamia (HuJI) is being suspected to be behind all the blasts, including the one that took place in February last year in Samjhauta Express connecting Delhi and Lahore [Images], agencies have not been able to find the culprits.

Serial blasts in Mumbai suburban trains also saw a dozen arrests but all of the accused have challenged the chargesheet in various courts.

'Leads' to the serial blasts in Jaipur in May this year that claimed 68 lives have reached a dead end despite the Rajasthan police coming out with various sketches of suspects.

Security agencies were shaken again within two months when coordinated blasts sent shock waves in Bangalore on July 25. These were followed a day after by the deadly explosions in Ahmedabad [Images] a day after that claimed 45 lives.

In Ahmedabad, police went to town saying that they had busted the entire module of SIMI [Images] responsible for various attacks in the country, but this claim has come into question with the Saturday evening's blasts.