An eight-year-old relative of the Bangladeshi prime minister was among more than 300 people killed in a wave of coordinated suicide bombings in Sri Lanka on Easter Sunday, according to reports in the country.

Zayan Chowdhury, who was also a relative of British Labour MP Tulip Siddiq, was having breakfast with his father at a hotel in Colombo when a suicide bomber detonated his device.

The child, who was the grandson of a cousin of the Bangladeshi leader, Sheikh Hasina, was among the 38 foreign nationals killed in the attacks, which left 321 dead and injured hundreds. Sri Lankans made up the vast majority of the dead.

Teenage siblings Amelie, 15, and Daniel Linsey, 19, were the latest British nationals to be named as victims in the blasts. The brother and sister died on the final day of their holiday while trying to escape the aftermath of the first explosion at Shangri-la hotel, according to multiple reports quoting relatives.

Sri Lankans have started to bury the dead in mass memorial services during a national day of mourning on the island, which targeted three churches and three luxury hotels. A local Islamist group, National Thowheeth Jama’ath, has been blamed for the attacks.

Three children of the billionaire fashion tycoon behind Asos also died. Anders Holch Povlsen, Denmark’s wealthiest man and one the largest landowners in Scotland, lost three of his four children. A spokesman for his company declined to give further details.

An Australian man whose wife and daughter were killed described his heartache after seeing them lying dead on the floor of a church. Manik Suriaaratchi and her 10-year-old daughter, Alexendria, were killed in the terrorist attack.

Sudesh Kolonne said he was outside the church when the bomb went off. “I heard a huge noise and I jumped into the church and I saw that my wife and my daughter were on the floor,” he told the ABC.

“I just saw my daughter on the floor and I tried to lift her up … she was already dead … exactly the same … next my wife is there.”