David Moorcroft of England ran a 55-second final lap and lopped nearly six seconds off the 5,000-meter world record during the Oslo Track and Field Games tonight.

Moorcroft was timed in 13 minutes 0.42 seconds, well inside the previous best of 13:06.20 set by Kenyan Henry Rono in Norway last September.

Later, American Steve Scott ran the second-fastest men's mile in history and Mary Decker Tabb, also of the United States, ran the second-fastest women's 3,000.

Scott, with a clocking of 3:47.69, failed by 0.36 seconds to break the world record of 3:47.33 held by Britain's Sebastian Coe. Tabb, timed in 8:29.72, failed by 2.6 seconds to surpass the 3,000 mark of 8:27.12 held by Ludmila Bragina of the Soviet Union.

Scott had won the mile in the Bislett Games here June 26 in the then-American record time of 3:48.53.

John Walker of New Zealand finished second in the mile tonight in 3:49.08 and Ray Flynn of Ireland was third in 3:49.77.

Moorcroft took the lead after 1,200 meters and moved steadily from the pack. His split times were 1,000 meters in 2:38, 2,000 in 5:12, 3,000 in 7:50 and 4,000 in 10:28.

Rono, who nearly broke his record last night in Stockholm, where he clocked 13:08.97, was unable to close in on Moorcroft.

But Moorcroft, 29, with a former best of 13:20.51, increased his speed almost every lap. Cheered on by 6,758 spectators at Bislett Stadium, he covered the last 400 meters in 55 seconds to break the record.

"The crowd was magnificent and meant a couple of seconds a lap," Moorcroft said. "I am too tired to be happy. It will take a day or two to understand I did it.

"I was afraid that I was running too hard and I felt the pain in my legs and in my chest with 1,000 meters left to go," he said. "I didn't hear the loudspeaker, but I heard the noisy, wonderful crowd and I knew I was close to the record."

Tabb, who missed by .57 of a second setting a women's mile record here June 26, finished far ahead of Wendy Smith of Britain, the runner-up in 8:46.01, in breaking her American 3,000 record of 8:38.73.

Steve Ovett of Britain failed to lower the world record in the seldom-run 2,000-meter race. He won in 4:57.71, 6.3 seconds off the world mark of 4:51.4 set by Walker here in June 1976.

Thomas Wessinghage of West Germany placed second in 4:58.42 and John Gregorek of Georgetown University was third in 5:00.19.