The total number of deaths in Scotland rose by a third between April and June 2020, according to official figures.
The National Records of Scotland (NRS) said 18,201 deaths had been registered, 4,515 more than the five-year average.
Covid-19 was the underlying cause in 3,739 of them, accounting for 83% of the excess deaths.
Deaths from diabetes, dementia and Alzheimer's were about a quarter higher than the five-year average during the three-month period, the NRS said.
Deaths from diseases of the genitourinary system also increased by 22.5%.
However, deaths from respiratory diseases decreased by 20.6% and deaths from transport accidents were down by 69.1%.
The three-month period covers the height of the coronavirus lockdown in Scotland when schools and businesses were closed, and traffic on all roads was significantly reduced.
Fewer marriages than five-year average
Julie Ramsay, vital events statistician for the NRS, said: "The Covid-19 pandemic has had a significant impact on the number of deaths we normally see at this time of year, and the overall death rate is a third higher than the five-year average.
"Covid-19 has also impacted the number of marriages - from April to June only 117 marriages took place, a stark contrast to the five-year average of 7,938."
Five of the marriages registered were same-sex marriages, a significant reduction compared with the five-year average of 286.
Ms Ramsay added that only 1,145 births were recorded as the registration of births was postponed during this period.
A large increase in the number of birth registrations is expected in the next quarter.