VIENNA, Jan. 13 (Xinhua) -- Renewed snowfall on Sunday intensified again the avalanche situation in the northern Alps, in which thousands of people were trapped, Austrian media reported.

In Salzburg, the entire Pinzgau Valley was closed Sunday afternoon as an avalanche threatened the only access road and some 5,000 people were cut off from the outside world, media reports said.

In Styria about 1,500 people were cut off from the outside on Sunday.

The Central Institute for Meteorology and Geodynamics (ZAMG) on Sunday issued the red warning level, the highest snow warning, for parts of the northern Alps from Vorarlberg to Lower Austria. The warning will probably remain in effect until Tuesday.

In Vorarlberg, three German skiers were killed and a fourth one missing, after they were struck by an avalanche late Saturday while skiing near the western Austrian city of Lech, local police said on Sunday.