Organised by the Hindu nationalist Bharatiya Janata Party (BJP) and its hardline ally Siv Sena, protest sit-ins will be staged in Mumbai as also in villages and towns across the western Indian province of Maharashtra.

The biggest protest is expected at Mumbai's Azad Maidan (Freedom Park), the site of many anti-British protests during the country's freedom struggle.

Protest sit-ins would be staged in Mumbai as also in villages and towns across the western Indian province of Maharashtra.

Dressed mostly in black, supporters of BJP and Shiv Sena already marched in a silent procession on Wednesday to protest the car bombings earlier this week.

Meanwhile, security remained tight across India in the wake of the blasts.

The twin car blasts – one in front of a tourist attraction and the other in a gold and jewellery market - was the worst in the city since 1993 when a series of explosions killed 260 people.

Though no one has directly claimed responsibility for the latest bombings, provincial authorities say they could have been in revenge of communal riots that rocked neighbouring Gujarat last year, killing at least 1,000 people.

Indian Deputy Prime Minister L K Advani has pointed his finger at the outlawed Students Islamic Movement of India, saying the outfit was a prime suspect.