New Delhi  - Three communist-ruled states in India shut down Thursday to protest the federal government's decision to hike the prices of petrol, diesel fuel and cooking gas, officials said.

Left-wing partners of the ruling United Progressive Alliance (UPA) said the price hikes of 9.5 to 17 per cent were "unjustified," demanded a rollback and launched weeklong protests on Thursday with a 12-hour dawn-to-dusk shutdown in the eastern states of Tripura and West Bengal and southern Kerala, which they govern.

Life came to a standstill in West Bengal and Tripura, where rail and air traffic was disrupted and scores of passengers stranded at airports and railway stations.

The eastern metropolis of Kolkata, West Bengal's capital, was the hardest-hit with no flights out of the city until late afternoon, a day after the price hikes were announced.

"Movement of trains has been hit in the states since early morning," DK Jha, spokesman for Eastern Railways told reporters. "We can only expect the trains to run on schedule after 6 pm when the strike ends."

Hundreds of passengers were stranded at the Kolkata airport.

"I had a flight to catch to Mumbai to get admission in an engineering college, but we are told that the protests may continue till tomorrow and I may lose my seat in the college," a student told the CNN-IBN news channel.

Like Kolkata, major roads in Tripura's capital, Agartala, were empty as public and private vehicles stayed off the roads in response to the strike.

Shops and markets were also closed in those states as were schools and colleges, which cancelled examinations scheduled for the next few days.

The shutdown was not as severe in Kerala, where train and air services functioned as normal.

But public transport and commercial vehicles stayed off the roads, and many shops and businesses were closed. Government offices also registered thin attendance.

Police said no major incidents of violence were reported from the three states but strike supporters had put up road and rail blockades in some places in West Bengal.

Communist politicians said the weeklong action would include rail and road blockades across the country, and similar strikes have been planned in the southern states of Andhra Pradesh and Tamil Nadu later this week.

Meanwhile, the West Bengal and Kerala governments announced they had reduced the sales tax on petroleum to soften the price hikes.

In a related development Thursday, Congress Party leader Sonia Gandhi asked Congress-ruled states to cut sales taxes and value added taxes on petroleum products.

The Congress Party-led UPA came to power in 2004, promising to alleviate economic hardships for the poor and farmers, but it has lost several key state elections, and surging inflation and now the fuel price hikes were expected to have a negative impact on its future electoral prospects.

A spate of state elections are scheduled over the next few months, and general elections are due in 2009. (dpa)