STOCKHOLM--British and Norwegian troops have surrounded 3500 Germans in a "final assault" on the iron ore port of Narvik, a Norwegian spokesman claimed tonight, and the jaws of another trap were reported closing on German-held Trondheim.

"Within a few days the entire Narvik region should be ours again," said the authorized Norwegian military spokesman in describing furious fighting in the full-force attack to wrest Narvik from the Germans.

The Norwegian military headquarters admitted that Hamar and Elverum in central Norway remain firmly in German hands. Previous unconfirmed reports had said that British-Norwegian forces had recaptured the towns.

The British and Norwegians were said to have isolated and surrounded large German units at three points around Narvik in a big drive that was unleashed suddenly late today while, 400 miles to the south along the ragged Norwegian coast, two British armies closed in upon Trondheim from the north and south.

Allied Tanks Inland

Inland, in the midlands belt north of Oslo, British and Norwegian troops supported by Allied tanks appeared on the basis of unofficial reports to be pushing the Germans back in bitter fighting southwest of war-wrecked Hamar.

The Norwegian military spokesman said 1000 German soldiers were isolated in the town of Narvik itself, 1500 at Gratanger, 25 miles north of the port where the Nazis were lured into a trap, and nearly 100 on the hills of Rombak Fjord jutting inland from Narvik.

The final assault on Narvik started after a warning had been broadcast to civilians by the British naval commander and leaflets had been dropped from airplanes saying that the Allies were ready to hammer the port from land, sea, and air to oust the Germans.

Civilians Flee

Civilians were advised to flee to the hills or hide in cellars. Many of them fled eastward toward the Swedish border as the radio blared its warning.

Before unleashing the assault from the north. It was stated, the British occupied Beisfjord behind Narvik and the fishing village of Falgerness as well as the lower part of the port to enable an encirclement.

The Germans were said to have been quick to respond to the encirclement and to have moved rapidly northward along the road to Tromsoe.

Norwegian troops, in the craggy hills along the route, allowed the Germans to advance 25 miles to Gratangen and then struck across the highway at Oesevatten at the Germans' rear, cutting off their retreat.

Norwegians Burn Towns

The Norwegian spokesman, who said his information came from a courier who reached the Swedish border from the Narvik zone, said the Norwegians set fire to the hotel and all other large buildings in Gratangen, leaving the town ablaze.

He said the capture of all the 1500 Germans isolated at Gratangen was anticipated, because the Norwegians have occupied all the strategic heights and control every avenue of escape.

"The Germans saw their predicament and tried to withdraw from the trap but it was too late," he related.

"The Germans, according to our latest courier reports, scattered to the few farm houses of the region to escape from the severe Arctic cold and Norwegian snipers dropped them in their tracks whenever they emerged from shelter."