MOSCOW, June 4 (Reuters) - Russia's Foreign Ministry summoned Nigeria's ambassador on Monday over the kidnapping of six Russian workers in the volatile Niger Delta.

"Today the Nigerian ambassador in Moscow will arrive at the foreign ministry for a discussion on this topic," Foreign Minister Sergei Lavrov, who is on a visit to South Korea, told reporters in televised comments.

Gunmen kidnapped the six Russians on Sunday and shot dead a local driver in a dawn attack on a residential compound of an aluminium company controlled by Russia's United Company RUSAL, the world's largest aluminium producer.

The kidnappers have contacted the Russian embassy in Nigeria by mobile telephone, Moscow-based Vesti-24 television reported. They said the Russians were in good health.

Lavrov said Russia was working with Nigeria and neighbouring countries such as Equatorial Guinea. A spokeswoman for Nigeria's ambassador said Dan Suleiman had gone to the Foreign Ministry.

Militants demanding regional control over the Niger Delta -- home to Africa's largest oil industry -- have stepped up attacks on oil facilities and kidnappings of foreigners since last year, but most abductions are by groups seeking ransoms.

The abduction of the Russians, who were working at the Aluminium Smelter Company of Nigeria (ALSCON) controlled by RUSAL, raised to 30 the number of foreigners held by different armed groups in the delta.

AlertNet news is provided by