Kiev: Ukraine vowed on Tuesday to use all weapons at its disposal to withstand an alleged new pro-Russian rebel advance that added urgency to a goodwill visit by Britain’s defence secretary.

Kiev accused the eastern separatist fighters of launching a another missile assault north of Mariupol — a government-held port that provides a land bridge between rebel territories and the Russian-occupied Crime peninsula.

“We will use our entire arsenal and all the means at our disposal to beat back the enemy’s assault,” Ukrainian military spokesman Vladyslav Seleznyov said.

“We cannot risk the lives of our soldiers,” said the top Kiev army representative. “The rebels used to launch Grad missile attacks on a rare occasion. Now, it is an everyday occurrence.”

The militias accused Kiev’s pro-Western forces of being responsible for the latest flare-up along east Ukraine’s 500-kilometre front.

A top insurgency leader accused Ukraine’s army of firing 500 mortar shells and rockets at rebel positions since Monday afternoon.

He reported the death of one militia member and a civilian in the separatist Donetsk province.

The two self-proclaimed republics of Donetsk and Lugansk launched their armed uprising shortly after the February 2014 overthrow of a Moscow-backed president in Kiev.

The clashes have killed more than 6,800 people and sent Moscow’s relations with the West crashing to their lowest point since the Cold War.

The crisis has also left 1.4 million people homeless and sent Ukraine’s economy — heavily dependent on exports from the country’s industrial east — into a tailspin.

The West is still pinning its hopes on a February truce agreement that has often been ignored but also kept fighting limited to a handful of flashpoints.

British Defence Secretary Michael Fallon met Ukrainian Prime Minister Arseniy Yatsenyuk in Kiev on Tuesday before travelling to the nationalist west of the former Soviet country.

“We will continue to stand shoulder to shoulder with you in the face of Russian aggression, in the face of Russian-directed insurgency and in the face of Russian-inspired terrorism,” Fallon said in comments dubbed over into Ukrainian by Kiev TV.

“The conflict has not settled into a frozen war: it is quite ‘red hot’,” he was further quoted as saying by Yatsenyuk’s office.

Fallon is due to oversee how British military trainers are progressing in their efforts to train around 650 Ukrainian soldiers for modern warfare.

The United States and Nato members have redoubled their efforts to prepare the poorly-equipped force for a possible invasion from Russia — a giant neighbour that denies any involvement in eastern Ukraine’s 16-month revolt.

Russia has called such Western steps as confrontational and staged its own war games along the Ukrainian border throughout the year.