Tensions between North Korea and South Korea are running high this week after Pyongyang sent a letter to the U.N. Security Council, repeating accusations that Seoul fabricated a September land mine incident, and after a North Korean howitzer was spotted close to the border.

A witness at an observatory in South Korea overlooking the heavily armed border on ?Monday confirmed the presence of a North Korean artillery piece positioned in clear view near the frontier.

South Korea’s ?Yonhap news agency on Sunday identified the weapon as a self-propelled 122-mm howitzer, saying its deployment near the border marked a rare public display of such artillery.