North Korea has fired a shell across the border into South Korea, prompting Seoul to respond with artillery fire, acccording to reports.

The North is believed to have been aiming at a loudspeaker in a border town that has been blaring anti-Pyongyang broadcasts recently, South Korean media said.

In response, South Korea fired tens of 155mm artillery roundsat the location where the shell came from, the country's defence ministry said.

KBS News, which is state-run, quoted a South Korean military official as saying that North Korea opened fire at around 4pm local time (7pm GMT) on the western front.

Yonhap said the shots did not cause any apparent damage and that there has been no response from Pyongyang to the artillery fire.

Soyth Korea's defence ministry said surveillance equipment detected the trajectories of suspected rockets and that it is investigating the incident.

"Our military has stepped up monitoring and is closely watching North Korean military movements," the ministry said in a statement.

There are no details on any of the injuries in the border town or in the North, but media outlets in South Korea reported that towns on the South Korean side of the border were being evacuated.

North Korea had promised to retaliate against the broadcasts, which criticise alleged provocations from Pyongyang and praising South Korea's democracy
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