The UK and European Union allies will support a new government in Ukraine "as and when that is formed", William Hague said today as power appeared to have slipped from president Viktor Yanukovych.
The Foreign Secretary and his German counterpart have held talks aimed at pushing for financial support for Ukraine as the constitutional crisis in the country deepened.
Mr Hague discussed the fast-moving situation with Frank-Walter Steinmeier and the pair agreed their support for a "new government" in the country, as President Viktor Yanukovych described the events as a coup and insisted he would not step down.
The sudden rush of developments left a power vacuum in the riot-hit country, and rendered pointless the peace deal signed by Yanukovych and the opposition the previous day.
Mr Hague said today that the voices of those who had been protesting would be heard.
"Today I am in close touch with key partners over the extraordinary developments in Ukraine," he said.
"Events in the last 24 hours show the will of Ukrainians to move towards a different future, and ensure that the voices of those who have protested courageously over several months are heard."
Agreed with German Foreign Minister Steinmeier today to support new government in #Ukraine and push for vital IMF financial package— William Hague (@WilliamJHague) February 22, 2014
Mr Yanukovych left the capital Kiev and travelled to his political powerbase in the country's east, while Ukraine's parliament has voted to call early presidential elections for May 25.
Protesters, curious locals and journalists from around the world flocked to the vacated presidential compound to see for themselves Mr Yanukovych's opulent villa, complete with a collection of historic cars, a wooden galleon and a private zoo, using social media to share photographs of the opulent building.
The amazing spectacle had been hidden behind huge walls and never seen by the public.
Matt Frei, of Channel 4 News, described "ornamental lakes, marble statues, deer and antelope cast in bronze."
The private zoo. Peacocks of course pic.twitter.com/pLNQ91w6rF— Matt Frei (@mattfrei) February 22, 2014
Знайшли біля причалу у воді документи pic.twitter.com/o1MYxFXoLa— Oksana Kovalenko (@superumka) February 22, 2014
Everybody taking pictures, people playing golf on the courts pic.twitter.com/JWSLIa4mM1— Olaf Koens (@obk) February 22, 2014
Under an agreement reached yesterday between Mr Yanukovych and leaders of the opposition protests, early elections were to be held no later than December.
But the possibility that he could remain in office for the rest of the year angered protesters who want his immediate departure.
A Foreign Office spokeswoman said Mr Hague's tweet about a "new government" referred to the changes agreed yesterday and "working towards a new constitution and elections".
She said the discussions with Mr Steinmeier were a follow-up to the developments yesterday.
"Obviously there is still a lot more to be done there now," the spokeswoman said.
"One of the things they talked about was the economic situation and putting together a financial package which will help to stabilise the situation in Ukraine, to enable the Ukraine to receive long-term support from the IMF."
Mr Hague said today the UK will work closely with its EU partners "in support of a new government in Ukraine, as and when that is formed."
"In the meantime it is important that Ukraine's political leaders respond to events calmly and with determination to harness the united efforts of all Ukrainians to work together for a successful future."
The party of former prime minister Yulia Tymoshenko - a rival to Mr Yanukovych - said that she had been released after two-and-a-half years in prison.
Addressing the crown in Kiev's Independence Square, Ms Tymoshenko paid tribute to the protesters who had lost their lives in the unrest, saying "heroes don't die, they are always with us and they always will be our inspiration".
Speaking from a wheelchair amid occasionally chaotic scenes in the square, which has become the focal point for the opposition movement, Ms Tymoshenko said the protests should continue.
"Until you finish this job and until we travel all the way, nobody has the right to leave," she said. "Because nobody could do it - not other countries, nobody - could do what you have done. We've eliminated this cancer, this tumour."
Mr Hague and his German counterpart Frank-Walter Steinmeier held talks aimed at pushing for financial support for Ukraine.
A Foreign Office spokeswoman said: "One of the things they talked about was the economic situation and putting together a financial package which will help to stabilise the situation in Ukraine, to enable the Ukraine to receive long-term support from the IMF."
A US State Department spokesman said: "Going forward, we will work with our allies, with Russia, and with appropriate European and international organisations to support a strong, prosperous, unified, and democratic Ukraine."
With Mr Yanukovych refusing to accept the will of the country's MPs, fears mounted that the country could split in two - a Europe-leaning west and a Russian-leaning east and south.
"They are trying to scare me. I have no intention to leave the country. I am not going to resign, I'm the legitimately elected president," Mr Yanukovych said in a televised statement.
"Everything that is happening today is, to a greater degree, vandalism and banditry and a coup d'etat," he said. "I will do everything to protect my country from breakup, to stop bloodshed."