BERLIN, JAN. 24 -- German firms illegally provided technology to help Iraq increase the range of its Soviet-designed Scud missiles, the weapons that have caused scores of casualties in Israel in the first days of the Persian Gulf War, a senior aide to Chancellor Helmut Kohl said today.

Lutz Stavenhagen, Kohl's top intelligence adviser, told reporters that the missile modifications took place in 1986 or 1987, but he did not name the companies involved.

Stavenhagen said the original range of the missiles was believed to be about 220 miles -- not sufficient to reach Israeli targets even from far western Iraq -- while some modified Iraqi versions now have a range of 500 miles. Tel Aviv, the Israeli city hit hardest by the missile barrage, is about 300 miles from suspected mobile-launch sites in the Iraqi desert near the Jordanian border.

State prosecutors have confirmed two separate investigations into support for Iraqi missile research by German firms, one based in the Westphalian city of Bielefeld and the other in the southern town of Stutensee.

In addition, a number of German companies are alleged to have aided the Baghdad government in chemical-weapons research, and at least 100 may have violated German law and U.N. sanctions by shipping sensitive materials to Iraq, according to the Economics Ministry. Turkey's President Turgut Ozal referred to German firms' alleged role in asserting that Germany has a special responsibility to help Turkey if it is attacked by Iraq. Germany refused this week to promise military aid to Turkey, a NATO ally.

Knight Ridder reported that Ozal told German television that NATO had defended West Germany against a Soviet threat for 40 years and said: "I think Germany has become so rich that it has completely lost its fighting spirit." The Bonn government has said its constitution prohibits the deployment of the German military beyond certain limits.