SEOUL (AFP) - North Korea has intensified screening and vowed "watertight" measures to ward off the Middle East Respiratory Syndrome (Mers) virus as an outbreak in South Korea killed 15 and sparked widespread alarm.

Officials have stepped up screening for and quarantine measures at the international airport and at border crossings, said Chosun Sinbo, a pro-Pyongyang newspaper based in Japan.

"Central and regional health officials are making thorough and watertight preparations to block any passage of the Mers virus into the country," it said.

Senior Health Ministry official Pak Myong Su, in an essay in the state-run Rodong Sinmun newspaper on Sunday, noted "growing concerns in a neighbouring country" about the outbreak. "We all have to actively join efforts to prevent Mers and to promote the superiority and capability of our socialist health system," he wrote.

Pyongyang has so far shown no sign of closing the only border crossing with the South, into the Kaesong joint industrial zone in the North.

But the isolated and impoverished country has taken drastic measures in the past to guard against viral diseases.

Last year it imposed a four-month ban on foreign tourists, purportedly due to concern at the spread of the Ebola virus.