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The US is holding its biggest anti-terrorism drill to test its response to biological and chemical attacks.

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More than 10,000 people are taking part in the five-day exercise which began on Monday.

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New Jersey is the setting for a simulated biological attack timed to coincide with a mock chemical attack in Connecticut.

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In Connecticut, people pretending to be victims lie near overturned buses as a result of the fake chemical attack.

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The aim of the exercise is to improve preparedness and identify weaknesses in the emergency response plan.

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The drill is also an opportunity for the authorities to test sophisticated bomb-detection equipment.