Actor Volodymyr Zelensky has cemented his position as Ukraine's leading presidential nominee about one month before the election, an opinion poll showed Monday.

Zelensky's approval rating rose to 25.1 percent in February from 19 percent in January, showed the nationwide survey conducted by the sociological group Rating.

Support for incumbent President Petro Poroshenko was up from 15.1 percent to 16.6 percent in February, while that for another front-runner, opposition politician Yulia Tymoshenko, shrank from 18.2 percent to 16.2 percent, according to the poll.

Former Ukrainian Deputy Prime Minister Yury Boyko placed fourth with 11.3 percent, while the remaining candidates each garnered less than 10 percent of support.

The survey was carried out on Feb. 19-28 among 2,500 adults and its margin of error is plus or minus 2 percent.

The presidential election in Ukraine is scheduled for March 31. To win the race in the first round, a candidate should earn more than 50 percent of the votes.

A record number of 44 candidates have registered to compete in the election, but last week two hopefuls, Andriy Sadovyy and Dmytro Gnap, said they would withdraw from the race. However, the country's Central Electoral Commission has not yet confirmed their withdrawal.