Harare - Police have arrested 71 people in Zimbabwe's border town of Beitbridge following angry protests over attempts to restrict imports, the state Zimbabwe Broadcasting Corporation (ZBC) reported on Saturday."Security has been beefed up" in the town, which is on the busiest border crossings in the southern African region, ZBC reported in a radio news bulletin.Protesters on Friday set a government warehouse on fire, looted a fast-food outlet, destroyed a house and vandalised traffic lights as tensions mount over a new requirement that traders obtain import permits for basic goods like jam and mayonnaise, according to a report in the state-owned Chronicle. With jobs in the formal sector hard to come by in cash-strapped Zimbabwe, many now depend on informal trading to boost their incomes.President Robert Mugabe's government is standing firm on the new regulations, with industry minister Mike Bimha denying claims circulating on social media earlier on Saturday that the ban - which is how many traders see it - had been overturned.Former information minister Jonathan Moyo went as far as to blame the protests on South Africa, saying in a tweet: "Even fools know the trouble was started not by importers in Zim but by exporters in SA who see Zim as a supermarket!"But not everyone will believe him. An economic crisis is worsening in Zimbabwe. The authorities have only been able to offer doctors and teachers a $100 advance on salaries due last month. In what will be a huge blow to the public health sector, the Zimbabwe Hospital Doctors' Association has announced members will no longer report for work because they "cannot put food on the table", according to The Zimbabwean website.