Research In Motion's BlackBerry services have improved significantly across Europe, the Middle East, Africa and India, the company said on Thursday, after a three-day global service outage hit millions of its customers.

Service levels are also progressing well in the U.S., Canada and Latin America and we are seeing increased traffic throughput on most services, although there are still some delays and services levels may still vary amongst customers, RIM said in an update on its website.

The company, however, said it cannot give an estimated time for the full recovery of services around the world.

On Wednesday, the company said it would eventually deliver all delayed email and instant messages to customers in five continents affected by the outage, but later told some of its corporate clients that it may not clear the huge backlog of messages until Thursday morning on the U.S. East Coast.

It apologized to customers in a statement on its Website and on its Facebook page.

The outage, the worst in about two years, adds to RIM's mounting problems, which include rising dissatisfaction with its co-chief executives and the company's inability to catch up with nimbler rivals like Apple. (Reporting by Devidutta Tripathy in New Delhi and Sayantani Ghosh in Bangalore; Editing by Sriraj Kalluvila)