Chicagoo, Dec 10 (IANS) Shackled and surrounded by federal marshals, Pakistani-American terror suspect David Coleman Headley, pleaded not guilty to charges that he planned the 2008 Mumbai terrorist attacks that killed 166 people.

Son of a Pakistani diplomat and an American socialite mother, Headley, 49, appeared Wednesday before US District Judge Harry Leinenweber in Chicago for an arraignment that lasted only about three minutes. He then was led away, guarded by a phalanx of federal marshals.

On his first court appearance since his October arrest by US authorities, Headley was clad in the bright orange jumpsuit of a federal prisoner and wore a grey sweatshirt under it.

Leinenweber set Jan 12 for the next hearing in the case.

During the routine arraignment, no new information was released by lead federal prosecutor Dan Collins. Headley, who changed his birth name from Daood Gilani to cover his tracks according to authorities, responded in a quiet voice to questions posed by Leinenweber.

Headley who was born in the US, but spent much of his childhood in Pakistan where he was raised by his Pakistani father, is cooperating with federal authorities.

Investigators believe he changed his name to Headley on the orders of Lashkar-e-Taiba, a Pakistani terror outfit, and conducted surveillance on potential targets in Mumbai that were eventually attacked by in a three day siege during Nov 2008.

One of Headley's court appointed attorneys, John Theis, said after the hearing that 'these are very serious charges', the ABC News reported.

They could result in imposition of the federal death penalty and because of that, a second court-appointed attorney has been added to Headley's defence team.

There did not appear to be any of Headley's family members in court. He is believed to be married to a Pakistani woman and father of four children. They were last known to live in a North Side Chicago apartment.

Meanwhile, FBI Director Robert Mueller came to Chicago Wednesday morning for a briefing on the Headley case and is expected to leave afterward, Chicago Sun Times reported.