A 92-year-old woman from Aizawl district succumbed to the infection around 6:30 pm on Tuesday, he said.
She was diagnosed with COVID-19 on June 2 and had been under home isolation, the official said.
The state now has 3,637 active COVID-19 cases, while 12,129 people have recovered from the infection, including 194 people on Tuesday.
According to the official, the 268 fresh cases detected from 2,443 samples tested in the last 24 hours, put the single-day infection rate at 10.97 per cent.
He said that 221 new COVID-19 cases were reported from Aizawl district, 16 from Lunglei, 12 from Kolasib, six each from Siaha and Lawngtlai, three each from Champhai and Saitual and one case from Mamit district.
More than 60 children and a healthcare worker were among the newly infected people, he said.
Six patients have travel history and the rest 262 were found to have locally contracted the infection, the official said.
As many as 129 patients have developed symptoms of COVID-19, while 136 are asymptomatic and reports of the remaining three are awaited, he added.
The recovery rate is 76.28 per cent and the death rate is 0.44 per cent.
The state has tested 4,38,999 samples for COVID-19 till date.
According to state immunisation officer Dr Lalzawmi, 3,14,844 people have been administered the first dose of COVID-19 vaccine till Tuesday and out of this 53,260 people have received both the doses.