The Deputy First Minister of Northern Ireland Martin McGuiness has urged Irish republican dissidents to end their violence on the 20th anniversary of the ceasefire by the Irish Republican Army.

McGuiness, a former IRA commander, said the groups should "take that same step into politics and away from conflict" and that there could be "no return to the violence and repression that scarred this society for so long".

"In 1994, dialogue offered the only way out of perpetual conflict and Irish republicans entered that dialogue confidently," he said in a speech in Derry, marking the anniversary.

"Successive agreements supported by the vast majority of the Irish people have removed any rationale for armed struggle and have put in place peaceful and democratic alternatives," he said on Sunday.

“the sovereignty, security and development interests of the country are at stake there is a need to proceed in a prudent and steady manner.”

"We should provide the Ukrainians with the type of defensive weapons that will impose a cost upon Putin for further aggression... This is no longer the question of some rebel separatists, this is a direct invasion by Russia. We must recognise it as that."

"I think that may very well be on the table right now. These are changed circumstances."

"Although they were surrounded and outnumbered, they held their ground for seven hours...We commend our soldiers for exhibiting resolve even while under heavy fire."

Iran’s President Hassan Rouhani has criticised new sanctions imposed by the US on the country as a “very ugly move”.

The president said Iran was still committed to continuing nuclear talks with the US and other countries, known as P5+1, despite the developments.

NATO as accused Russia of breaching Ukraine’s sovereignty by directly supporting rebels in the east of the country.

Secretary-General Anders Fogh Rasmussen, speaking after an emergency meeting with NATO ambassadors, said that "despite hollow denials", it was clear that Russian forces illegally crossed the border into Ukrainian territory.

"This is not an isolated action, but part of a dangerous pattern over many months to destabilise Ukraine as a sovereign nation," he said.

"This is a blatant violation of Ukraine's sovereignty and territorial integrity. It defies all diplomatic efforts for a peaceful solution."

Rasmussen called on Russia to halt all military action and supporting the rebels, and to take “immediate and verifiable steps towards de-escalation of this grave crisis".