The leaders of South Korea and the United States agreed Tuesday on strengthening the allies' combined defense posture to counter North Korea's persistent provocations, a day after it fired four ballistic missiles towards the East Sea, Seoul officials said.

During their 20-minute telephone talks, South Korea's Acting President and Prime Minister Hwang Kyo-ahn and US President Donald Trump shared the need to sternly deal with the North's latest launch. They cast it as "not only a breach of UN Security Council resolutions, but also a provocation against the international community," Hwang's office said.

Trump, in particular, pointed to the need for closer bilateral cooperation in coping with North Korea issues, including its missile provocations, through in-depth discussions at future two-way high-level meetings.

Hwang, for his part, stressed that the allies have to strengthen their deterrence against the wayward regime and work together to end its nuclear ambitions.

Pyongyang's latest provocation came less than a month after the regime fired off a new intermediate-range ballistic missile.

The launch is seen as the communist regime's response to the allies' ongoing military drills and their accelerating move to install a US missile defense system in South Korea. Some observers say the launch is also intended to affect Washington's ongoing efforts to formulate its policy toward the North. (Yonhap)