Leo Dacaynos, a member of the Samar's disaster management council, said on DZBB radio that 300 people were confirmed killed in Basey, a small town on Samar.
He said almost 2,000 other people were missing in Basey and other Samar towns.
This was the first confirmation of large-scale fatalities in the island of Samar after Haiyan made landfall on the island before dawn Friday.
However vast areas of Samar, an island of over 733,000 people, still have not been contacted over two days after the typhoon struck.
Authorities estimate that more than 10,000 were killed by the storm in the neighbouring island of Leyte and the death toll in other typhoon-hit areas is rising further as well.
Another place particularly hard hit was the city of Tacloban, capital of Leyte province, where some 400 bodies have been recovered. Initial estimates are that as many as 10,000 people in the city - population 200,000 - may have died.
With Haiyan due to hit Vietnam's coastline tomorrow, 600,000 people have been moved to shelters or higher ground as that country braces for the super typhoon's arrival.
"We have evacuated more than 174,000 households, which is equivalent to more than 600,000 people," an official report by Vietnam's flood and storm control department said today.
The storm is expected to strike on Monday morning after changing course, prompting mass evacuations in northern Nghe An province around 230 kilometres (145 miles) from the capital Hanoi, the update said.
With the change in direction, many of the estimated 200,000 evacuated in four central provinces yesterday have been allowed to return to their homes.