UPDATE 6-Singapore's ruling party seen retaining power, but opponents make gains

* Ruling PAP ahead in majority of seats after early counting

* Opponents increase vote share in several districts

* Deputy PM in close-fought constituency race (Recasts with early results)

By Jessica Jaganathan, Fathin Ungku and Anshuman Daga

SINGAPORE, July 11 (Reuters) - Singapore's ruling People's Action Party is on track to retain power comfortably, early counting of votes from Friday's general election showed, but it appears to have suffered a swing against it in a poll held under the cloud of the COVID-19 pandemic.

In power since independence in 1965, the PAP had been widely expected to win and carry Prime Minister Lee Hsien Loong to what is likely his last victory before retirement as national leader.

A random sample of 100 votes from each polling station showed the PAP retaining more than two thirds of seats in parliament, according to the Singapore Elections Department.

Several districts reported close-run races, including a constituency being contested by Deputy Prime Minister Heng Swee Keat, who was earmarked to take over as the city-state's leader from PM Lee the coming years.

The PAP's polling appeared "off the pace", said Eugene Tan, a professor at Singapore Management University (SMU) and ex-member of parliament. The main opposition Workers' Party was seen adding to its existing six seats in parliament.

The PAP won almost 70% of the popular vote in 2015 and secured 93% of seats in parliament.

(Reporting by Jessica Jaganathan, Anshuman Daga, Fathin Ungku, Tom Westbrook, Christian Schmollinger, John Geddie and Aradhana Aravindan; Editing by Simon Cameron-Moore, Kevin Liffey and Nick Macfie)