Pirates attacked a cargo vessel off the coast of Nigeria and kidnapped two crew members, a maritime expert confirmed Thursday, in the latest high-seas strike in the Gulf of Guinea.

The CMA CGM Turquoise, managed by Dioryx Maritime Corp. in Greece, was stormed late on Monday as it travelled between Nigeria's commercial hub Lagos and Douala in Cameroon.

It was the second attack in one day: early Monday pirates kidnapped six crew members of a Turkish cargo ship, the M/T Puli, according to the Nigerian Navy.

‘This attack -- like most others off the Niger Delta -- was carried out at night and carried an element of surprise,’ Dirk Steffen, from the Denmark-based Risk Intelligence firm, told AFP, referring to the later attack.

‘The crew mustered in the citadel after the attackers had boarded the ship, but two crew members -- the Filipino 2nd officer and the Egyptian electrician -- did not make it there in time and were seized by the attackers’, he said in an email.

The Liberian-flagged vessel, chartered by French shipping company CMA CGM, was attacked at 8:56 pm (1956 GMT), 28 nautical miles from the coastline of the oil-rich Niger delta region.

Steffen, the director of maritime security at Risk Intelligence, said the target was unusual and indicated the pirates were aiming at kidnapping rather than hijacking tankers for their fuel cargo.

The Gulf of Guinea is increasingly becoming a piracy hotspot and Risk Intelligence has recorded 32 offshore attacks for Nigeria alone this year.

Steffen linked the increase to the winding down of an amnesty scheme to former Niger Delta militants, who demanded a fairer share of oil revenue through kidnapping and sabotage in the 2000s.

It also reflected a trend of a decrease in abductions and offshore piracy in the region around elections. Nigeria held presidential and parliamentary polls last year.