Internet access across several East African countries was disrupted on Sunday due to damaged undersea cables, global web monitor NetBlocks said.

Tanzania and the French Indian Ocean island of Mayotte were the hardest hit, the internet surveillance group said.

"The incident is attributed to failures affecting the SEACOM and EASSy subsea cable systems," it said on X, formerly Twitter, referring to submarine communications cables that connect the region.

The faults were on cables between Mozambique and South Africa, according to Tanzania's information and technology minister Nape Nnauye.

Mozambique and Malawi were seeing a medium impact while Burundi, Somalia, Rwanda, Uganda, Comoros and Madagascar had less severe outages, NetBlocks said.

West African nation Sierra Leone was also affected.

Services had been restored in Kenya, NetBlocks said but many users reported patchy connectivity.

Kenya's biggest telecoms operator Safaricom said it had "activated redundancy measures" to minimise the interruption.

"You may, however, experience reduced internet speeds," it told its users on X.

Most of the world's internet traffic passes through scores of fibre optic cables laid along seafloors, with one of the longest, at 15,000 kilometres (9,300 miles), stretching from Portugal to South Africa.

In 2009, SEACOM launched Africa's first fibre-optic cables connecting the eastern and southern coasts, according to its website.

Several West and Southern African countries suffered similar outages in mid-March because of damage to the cables.