First the Greek-owned MV Nipayia, a 9,000-tonne tanker with a crew of 19, was seized on Wednesday.
Then the 23,000 MV Bow-Asir, a Norwegian-owned chemicals and oil tanker with 23 people on board, was captured earlyon Thursday off the Somali port of Kismayo, infamous as a pirates' haven.
More than 130 merchant ships were attacked in the area in 2008, according to the International Maritime Bureau, with most of them eventually being freed, along with their crew, after ransoms were paid.
Attacks on shipping had decreased slightly since the beginning of the year, after the high-profile seizure of the Sirius Star, an enormous tanker more than 1,000 feet long and with a capacity of more than two million barrels of oil.
The ship was released in January after a ransom was handed over, but the incident coincided with the deployment of an EU antipiracy naval mission, along with an increased presence in the area by the US Fifth Fleet, which is based in Bahrain.
Nonetheless the double seizure shows the difficulty of securing a vast area of open ocean, despite its being one of the world's most important trade routes.
In the wake of the Sirius Star takeover, and with insurance premiums rising, a number of shipping companies said they were ordering their vessels to avoid the area, sailing all the way around Africa rather than passing through the Suez Canal on their way to and from Europe.
The move inevitably put up the costs of transporting goods, which will ultimately be paid for by European consumers.
Pirates in Somalia have seized two European tankers within twenty-four hours. In the same time frame three other vessels escaped and a yacht which disappeared after departing the Seychelles has been reported as hijacked.

Yesterday MV ''Nipayia'', a 9,000-ton tanker owned by Athens, Greece-based Lotus Shipping and flagged in Panama, was seized. The vessel has eighteen crew members from the Philippines and a captain from Russia. She was hijacked 380 miles from Hobyo.

Early today the MV ''Bow Asir'', a 23,000-ton oil and chemicals tanker, was also seized in the same area, a 750,000 square mile ocean expanse near the Gulf of Aden. The vessel is owned by the Isle of Man's Star Tankers and is managed by Norwegian firm Salhus Shipping. There are conflicting crew numbers of 23 or 27 crew on board, but it is known that five of these are Polish and the captain is Russian.

Salhus was alerted at 0729GMT by the Bahamas-flagged ship that two small boats were chasing the vessel; at 0745GMT another message said they had boarded and three hours later an email confirmed the ship had been seized. There are sixteen to eighteen pirates on board, armed with machine guns.

The Seychelles' state broadcaster reported yesterday that a small yacht from the islands is thought to have been seized. The ''Serenity'', with two people from the Seychelles on board, departed the nation on February 28 and headed into the Indian Ocean. The ship never arrived at her destination of Madagascar. Nothing has been heard from the ship since she left port.

Three other ships were also targeted in two separate failed attacks yesterday. At 0907GMT MV ''Explorer III'' and MV ''Ocean Explorer'' stated that two small boats were chasing them. The ships were able to outrun the pirates. Later, at 2055GMT, the MV ''FD Gennaro Aurilia'' increased speed after a fishing boat began to approach. The master radioed nearby warships for help, after which the boat turned off its light and retreated.