BEIJING, CHINA - Authorities in one of China's biggest cities vowed Tuesday to crack down on violence that has marked a rare strike by taxi drivers, and called for an immediate return to work.

Several thousand taxi drivers extended a strike in the urban areas of the southwest Chinese city of Chongqing, home to over five million people, after cabbies smashed taxis Monday that had continued operating.

"If these incidents occur again, the public security organs will adopt a firm attitude and take firm measures," the website of the official Chongqing Daily quoted an unnamed city official as saying Tuesday.

"We will crack down hard on any illegal activities that impair the normal operations of taxis and we will safeguard the legal rights of operators."

The official apologised to angry citizens over the disruption in taxi services and the violence that occurred.

Drivers said Monday that they were striking over high operating costs, low fares, high traffic fines and widespread fuel shortages.

They are also unhappy over the government's failure to rein in unlicensed taxi operators who they say are stealing fares.

In response, the government has agreed to increase supplies of fuel to the city's taxi drivers and crack down on unlicensed cabs, while also agreeing the minimum fare of five yuan (S$0.73) is too low, the city official said.

"All the taxi companies in urban areas are firmly supporting the measures adopted by the city government to resolve the issue," he said.

He said the companies promised to try to persuade drivers to resume normal taxi operations Tuesday.

Beside the low fares and rising fuel costs, the taxi drivers must also pay companies between 380 yuan and 440 yuan a day to lease cars, Xinhua said.

The government has agreed that such fees would be reduced by up to 70 yuan per day, but a detailed plan has yet to be worked out, it added.

The report said that about half of the city's nearly 9,000 urban taxi drivers had returned to work by Tuesday afternoon.

However, most of the cab companies contacted by AFP refused to comment other than saying their cabbies were still striking.

Two cab companies said that most of their taxis had returned to work, but some drivers remained on strike.

"We have seen the government notices and after some discussions we decided to return to normal operations," a manager at the Chongqing Hongqiao Taxi Company told AFP.

"It will take some time to resolve these problems... Most drivers have returned to work but others want to watch to see if things improve."

Monday's violence was largely aimed at drivers who crossed picket lines and refused to join the strike. Over 100 taxis had been smashed as well as three police cars, Xinhua said.