This undated picture shows South Korea's Cheonan naval ship in South Korea, Friday, March 26, 2010. South Korea's military scrambled Cheonan naval vessels to the western waters near the disputed maritime border with North Korea late Friday after an explosion ripped a hole in the bottom of a military ship, officials and news reports said. [Xinhua/AFP]

The rescue operation to search for the 46 missing sailors in South Korean ship sinking is still under way on Saturday, Seoul's Yonhap News Agency reported.

The operation has been interrupted by strong currents in the Yellow Sea, but 18 more special rescue workers were committed to the rescue operation in Saturday afternoon as weather conditions gradually improved, according to local media.

So far, 58 out of the 104 crew members aboard the 1,200-ton ship that sank late Friday off the west coast of the Korean Peninsula have been rescued, with two of them hospitalized for minor cerebral hemorrhage.

A South Korean naval ship, the Cheonan, sinks near South Korea's Baeknyeong Island, close to North Korea, in the western waters on Saturday, March 27, 2010. [Xinhua/Reuters]

The patrol ship, named Cheonan, sank near the country's northernmost island of Baekryeong after an unidentified explosion in the back of the ship made a hole in the bottom of it, local media reported citing military officials. Another South Korean naval ship fired at an unspecified object northward in a following action.

The cause of the incident is unknown yet and President Lee Myung-bak demanded at the second emergency meeting with security officials earlier in the day a "quick and thorough" investigation and rescuing the missing by all means.

Lee also ordered related nations engaged in the six-party talks be informed of proper information about the incident while urging government agencies to take measures to reassure the public, Presidential Office spokeswoman Kim Eun-hye said at a press briefing after the meeting.

Kim added that there are no special movements by the Democratic People's Republic of Korea (DPRK) so far.

The unidentified target a separate South Korean vessel fired at could have just been a flock of birds, according to media reports.