North Korea fired seven ballistic missiles on Saturday, South Korea’s Defence Ministry said, in an act of defiance toward the US that further stoked regional tensions already high due to its nuclear test in May.

South’s Yonhap news agency said the missiles were “Scud-type”, marking an escalation of recent saber-rattling by the reclusive North, which has fired several non-ballistic, short-range missile since the May 25 nuclear test.

It was the biggest barrage of ballistic missiles the North has fired since it launched seven missiles in 2006 around the US July 4 Independence Day holiday, including its longest-range Taepodong-2.

The launches came as the United States has cracked down on firms suspected of helping the North in its trade in arms and missiles.

An anonymous South Korean official quoted by Yonhap said the launch may have been intended to send a message to Washington, the North’s main foe who for years has been trying to press Pyongyang to end its atomic ambitions and rein in missiles that threaten US allies South Korea and Japan.