BERLIN - Six crew from a German container vessel have been kidnapped in Nigerian waters, a shipping company said on Tuesday.Four of those taken are Filipino, and one is a Ukrainian national, according to the Philippines department of labor and Ukrainian foreign ministry.Kidnapping for ransom is a common problem in parts of Nigeria. A number of foreigners have, in the last few years, been kidnapped in the Niger Delta, source of most of the crude oil which is Nigeria's economic mainstay."The vessel was attacked by pirates on early Saturday morning when it was approaching one of the ports of Nigeria," said a spokesman for Peter Doehle Schiffahrts KG."Six of the crew were taken off the ship and they are now held by kidnappers in Nigeria," he said. There were no German nationals among the kidnapped but the spokesman declined to say where those abducted were from.Those kidnapped comprise four Filipinos, one Ukrainian and one Hungarian, officials from the countries involved told Reuters.At the time of the statement there was no official contact with the kidnappers and the vessel had moved away from Nigerian waters with the 12 remaining crew safe, the spokesman said."The top priority is to try and establish contact with the kidnappers and try to have a quick and safe release of our seafarers," he said.Germany's foreign ministry did not immediately respond to an email seeking comment.Four of the six abducted crew members are Filipinos, the Philippines labor secretary told Reuters.An official at Ukraine's foreign ministry said preliminary information indicated a Ukrainian citizen was among those kidnapped. He gave no further details.One Hungarian national was also taken, a person familiar with the matter told Reuters, speaking on condition of anonymity because of the sensitivity of the rescue operations.The Hungarian foreign ministry did not immediately respond to a request for comment.