N. Korea upgrading rocket launch site: Report

WASHINGTON (AP) - A US research institute says North Korea is upgrading one of its two major missile launch sites, apparently to handle much bigger rockets.

Design features of a new launch pad under construction at the north-eastern site of Tonghae also suggest that Iran may be helping North Korea.

38 North, the website of the US-Korea Institute at Johns Hopkins School of Advanced International Studies, published its assessment on Thursday based on commercial satellite images, the latest taken last month.

The analysis also identifies activity at an older launch pad at Tonghae, last used for a long-range rocket in 2009, but says it is unclear if that indicates preparations for another launch there.

A successful satellite launch in December and a nuclear test on Tuesday have intensified international concern over Pyongyang's weapons development.