Authorities in Seoul are verifying the reports of sounds of artillery fire heard around Yeonpyeong Island in the Yellow Sea. It is yet to be determined where the firing originated from.

South Korean army officials claimed that the sound of firing was heard twice since Friday afternoon. There have been no reports of any damage yet, but authorities maintain that a thorough search of the area is currently underway.

There were reports of sounds of artillery fire inside the North's territory off the island and we are checking them, the Yonhap News Agency quoted an official for the South's Joint Chiefs of Staff.

The reports of firing also come in the wake of the North issuing fresh warning to South and its ally, the United States. The warning released through its official Korean Central News Agency (KCNA) threatened a 'shower of dreadful fire,' if its sovereignty was violated. South Korea and the U.S. have agreed to hold joint drills at Yeonpyeong Island in a show of force.

The army and people of the DPRK are now greatly enraged at the provocation of the puppet group while getting fully ready to give a shower of dreadful fire and blow up the bulwark of the enemies, North Korea said.

Gone are the days when verbal warnings are served only, the KCNA reported. It also warned the United States not to side with Seoul and added that their actions were 'little short of feeding oil to the fire.'

Two soldiers and two civilians were killed while several others were injured as North Korea fired artillery shells at a South Korean island Yeonpyaong Island in the Yellow Sea on Tuesday. The Island located near the West Sea inter-Korean border has often been a place of military hostility between the both the nations. Pyongyang and Seoul have blamed each other for setting off the artillery attacks.