United States has temporarily closed its embassy in Ukraine's capital Kyiv due to a credible threat of a significant air attack on November 20. The US State Department issued a security alert, advising American citizens to take immediate shelter in case of an air raid siren.

This comes a day after Ukraine fired US-supplied ATACMS missiles on targets within Russia following the Joe Biden administration's go-ahead.

Ukraine's military intelligence agency claimed responsibility for a recent strike on a Russian command post in the Belgorod region, bordering Ukraine. The specific weapon used in this attack remains undisclosed.

The Russian government has responded strongly to these developments, issuing threats of retaliation and warning of potential nuclear consequences. 

In response to the escalating situation, the UK government has initiated a thorough review of the security measures for its diplomatic personnel in Kyiv. 

Science Secretary Peter Kyle emphasized the need for de-escalation from Russia to bring the conflict to an end. Kyle stated, "We are looking at the situation incredibly closely. We have very good relationships with the government in Kyiv and with the United States. We will do everything we can to keep British citizens safe."

Despite Russia's continued nuclear threats, UK Labour leader Keir Starmer reiterated the UK's unwavering support for Ukraine. 

Starmer said, "We will continue to support Ukraine, even in the face of irresponsible nuclear rhetoric from Russia."