Thai Army chief General Prayuth Chan-ocha said today that martial law will remain in place until "peace and order has been restored" in the country.
The Thai Army will deal with anyone who uses weapons and harms civilians, he told a news conference today, adding that opposing political groups should "talk to each other".
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Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.
A wet, wintry night in places with rain and hill snow slow to move away from southern Scotland and northern England.