New Delhi, May 31 (IANS): Terrorism has to be fought on all fronts and not selectively, Prime Minister Manmohan Singh said Tuesday.

The prime minister told a news conference also addressed by German Chancellor Angela Merkel here that terrorism posed "a serious challenge" to the world.

But it "has to be fought on all fronts and not selectively", he said, in a message clearly directed at the US.

Manmohan Singh said that he and the German chancellor discussed the situation in the Middle East and North Africa, including the Libyan unrest and their impact on global peace and security.

Afghanistan and Pakistan also figured in the discussions during the chancellor's day-long visit, her second to New Delhi since 2007, he said.

"We have had very useful and wide-ranging discussions," he said.

Manmohan Singh sought greater German investment in India, particularly in the areas of infrastructure, high technology, energy and basic applied sciences.

India, he said, "offers a stable and friendly investment climate".

Germany is New Delhi's largest trading partner in Europe and is among the largest foreign investors in India.