Indian authorities say they have arrested man accused of helping to plot Mumbai attacks in 2008

The authorities in Delhi say they have arrested an Indian citizen accused of helping to plot the 2008 Mumbai attacks. It raises the prospect that investigators may finally be able to answer many outstanding questions about the militant attack that left more than 160 people dead.

Foreign minister SM Krishna confirmed that police were questioning Sayed Zabiuddin, also known as Abu Hamza. It is alleged that Hamza helped teach Hindi to the 10 Pakistani militants who carried out the attacks of November 2008 and helped guide them during the assault.

Indian media today played a recording made by the intelligence services of a telephone conversation between militants who laid deadly assault to a Jewish centre in the city and their handlers in Pakistan.

Part of the conversation is said to feature the voice of Hamza who tells the militants: “This is just the trailer, the film has yet to start rolling.”

The attacks by members of the Pakistan-based Lashhar-e-Taiba (LeT) group stunned India and set back the relationship with its neighbour by several years. The Indian authorities are still battling to persuade Pakistan to launch legal proceedings against several people it says were ring-leaders, among them Hafiz Saeed.

Mr Saeed was initially brought before a court but released for lack of evidence, say Pakistani officials who say India must provide more compelling information. Although Mr Saeed lives openly in Lahore and regularly delivers speeches denouncing both India and the US, in May US Secretary of State Hillary Clinton issued a $10m reward for information leading to his capture.

Police said that Hamza, who was born in the central state of Maharashtra, was detained at Delhi’s international airport last Thursday but have released few other details. Home minister P Chidambaram refused to comment on reports that claimed that Hamza had been deported to India from Saudi Arabia. There was no comment last night from Saudi officials.

Vikram Sood, a commentator who formerly headed India foreign intelligence agency, the Research and Analysis Wing (RAW), said if it was Hamza who had been detained it marked an important breakthrough.

“This would be a significant step forward because it would provide investigators with someone close to the heart of the operation,” he said. “There are so many questions about the 26/11 attacks. The main reason for that is the lack of co-operation from across the border.”

Mr Krishna was asked yesterday what approaches might now be made to Pakistan, following the arrest of Hamza. According to Reuters, he replied: “Let the Delhi police go through the investigation first, and then they will send a report to the government. And then we will certainly see what appropriate ... action can be taken.”

The attacks of 2008, in which the militants laid siege to luxury hotels, a train station and a Jewish community centre, brought parts of India’s commercial capital for a standstill for three days.  Of the 10 LeT militants, just one, Ajmal Kasab, was captured alive. He has been found guilty of a series of charges including waging war against India and sentenced to death. It was apparently during questioning of Kasab, that police learned of the identity of Hamza.