Thailand has extended tighter containment measures in the capital and high-risk provinces probably until the end of August in a bid to slow the spread of Covid-19 as the country deals with its biggest outbreak to date.

Thailand has reported 18,027 infections and 133 deaths, bringing the cumulative total to 615,314 cases and 4,990 fatalities, mostly from an outbreak since April that is being fuelled by the highly transmissible Alpha and Delta variants.

The restrictions, including travel curbs, mall closures and curfews, will be expanded to 29 provinces classified as "dark red zone" from 13, Apisamai Srirangsan, spokeswoman for the government's Covid-19 task force, told a televised news briefing.

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