"Currently, the China-Russia comprehensive strategic cooperative partnership is at the best level in history, which sets an example for building a new type of worldwide relations", Xi said in a message to Putin.
Prime Minister Theresa May's office says the National Security Council met Tuesday to discuss the poisoning of Sergei Skripal and his daughter Yulia.
German Chancellor Angela Merkel wished Putin success and called for more dialogue. Each has expelled 23 of the other's diplomats as their relations have sunk to a post-Cold War low.
Her comments followed strong words from Boris Johnson, who accused Russia of trying to hide "the needle of truth in a haystack of lies" over the case - after Mr Putin dismissed the idea of Russian responsibility as "nonsense".
However, the European Union said "violations and shortcomings" in the election flouted global standards, pointing to one-sided media coverage and curbs on political freedoms.
"We stand in unqualified solidarity with the United Kingdom in the face of this grave challenge to our shared security", the draft leaders' statement says.
However, Ella Pamfilova, head of the Central Electoral Commission, said there were only half as many reported violations compared to 2012, and that none had been serious.
Communist candidate Pavel Grudinin was second with 2.32 percent of votes, followed by Vladimir Zhirinovsky from the ultranationalist Liberal Democratic Party with 0.92 percent of votes and Ksenia Sobchak from the Civic Initiative with 0.73 percent of votes. Some of calls are taking place now, we will inform you accordingly, " the spokesman said.
Kremlin spokesman Dmitry Peskov said on a phone call with reporters that Moscow does not regard this as an unfriendly act.
Putin has similarly denied any collusion, saying in December that such accusations showed a "lack of respect" for the voters who supported Trump. "I see trust and hope in this; hope among our people that we will continue to work just as intensively, just as responsibly, and even more effectively", he said.
However, French President Emmanuel Macron raised the poisoning of an ex-spy in Britain with him.
Russian Federation has fiercely denied any involvement, saying that it had destroyed its chemical weapons and had no motive to kill Skripal, who was convicted of spying for Britain but released in a 2010 spy swap.
"Falsifications, eliminations of political opponents, Kremlin-controlled media leave no chance to anybody except Putin", Pussy Riot alleged in a statement released alongside the three-minute-long track.
The constitution limits the president to two successive terms, obliging him to step down at the end of his new mandate.