Police in Zimbabwe have fired tear gas and warning shots at demonstrators as a strike against the government's economic policies closed businesses and crippled public transport.

Wednesday's strike, named "stay-away day", followed days of unrest over the government's failure to pay civil servants' salaries, a currency shortage, import restrictions and police road blocks that were allegedly extorting cash from commercial drivers.

"This is a sign of economic collapse wich has left people with nothing more to sacrifice and nothing to lose," Dumisani Nkomo, spokesman for the Crisis in Zimbabwe Coalition campaign group, told the AFP news agency.

"We are heading towards a tipping point as a country, where citizens will express their pain by any means."

There were few people on the streets of the usually bustling capital Harare after civil society organisations called for the strike to pressure President Robert Mugabe into tackling economic woes.

In some suburbs of Harare, protesters burned tyres and blocked streets to prevent cars from heading into the city centre.

Police fired tear gas at small gatherings of people, the main bus ranks were deserted and commuters stranded.

The Zimbabwe Lawyers for Human Rights (ZLHR) group said police had arrested at least 20 people across the country.

The police issued a statement condemning violence and Assistant Commissioner Charity Charamba said at least 19 people were arrested in Harare.

The commissioner also said that in Bulawayo, Zimbabwe's second largest city, a man had been arrested for the possession of "homemade petrol bombs".

In Matabeleland North, a western province, at least 17 people were arrested for "staging an unlawful demonstration", Charamba added.

One garage owner in Harare told Al Jazeera that police had come to the premises and beat him and his staff with sticks.

Dirk Frey, of the Occupy Africa Unity Square opposition movement, said the protests were a success.

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"Despite sporadic incidences of violence, all over the country people have responded to the call. The state's crackdown in response, however, is of concern as it is a violent way of silencing people," he said.

The strike was the latest in a series of protests against Mugabe's government. Such protests are rare in Zimbabwe.

Additional reporting by Tendai Marima in Harare. Follow her on Twitter @i_amten