German customs investigators said Thursday they had seized their largest-ever haul of illegal pharmaceuticals -- 3.5 million pills from India, mostly slimming and sexual potency "lifestyle drugs".

The black market value of the smuggled drugs -- sold in "brisk, illegal Internet trade" and also including painkillers, sedatives and anti-depressants -- was around 14 million euros ($15.8 million), customs officials said.

Four Germans, aged 25 to 65, and one Dutch national, 34, were arrested, and police also confiscated 440,000 euros in cash as well as two cars and several luxury watches.

The seizures, carried out in some 20 raids on homes, flats and garages earlier this month, were the largest such bust in Germany, customs officials from North Rhine-Westphalia state said in a statement.

"The seemingly low prices, the simple 'prescription-free' ordering, the online payment and home delivery tempt many consumers to buy these drugs on the Internet," one investigator said.

"In fact, though, they are risking their health because no-one knows what the ingredients and dosages are. On top of that they are unwittingly supporting organised crime."