MOSCOW -- Russian diplomats and their families climbed aboard buses and left their embassy in Washington on Saturday while across the Atlantic, American envoys took down the flag from outside the U.S. Consulate in St. Petersburg, loaded up boxes, closed the office down and headed home.

The moves were the latest in a spy poisoning case that has escalated East-West tensions, with both sides expelling more than 150 of each other's diplomats from two dozen countries.

Britain has insisted that the Russian government was behind the nerve agent poisoning of a former Russian spy and his daughter March 4 in the English city of Salisbury, a charge the Russians vehemently deny.

The Tass news agency says all of the 60 Russian diplomats ordered out of the United States were heading for a homebound flight on Saturday night.

In St. Petersburg, workers at the U.S. consulate hurried to meet the Saturday deadline to close the consulate, imposed by Russia just two days earlier. In brief comments to reporters, U.S. Consul-General Thomas Leary said "we are ready to leave."

A truck with bags and boxes left the consulate in the late afternoon, its driver waving and honking his horn several times. Outside the elegant 19th-century building, someone had placed four yellow tulips and a card from neighbours reading "hope to see you again."

City workers came to inspect the building late Saturday, but it was not clear if all the staff had departed.

Russians watching the activity expressed mixed views on the consulate's closure.

"The American side always knows that we can strike back if we are attacked," said Valentina Petrova, 77.

But 24-year-old Artem Zykov saw it differently.

"Russia should have found different mechanisms to respond without such radical measures," Zykov said.

British officials, meanwhile, said Saturday the government is considering Russia's request for access to the daughter of the former Russian double agent. Russian officials insist they have a legal right to see 33-year-old Yulia Skripal, who lived in Moscow and was visiting her father, Sergei Skripal, in Salisbury when they were attacked with a nerve agent that apparently came through his front door.

The Foreign Office said it was reviewing the Russian request "in line with our obligations under international and domestic law," adding that the government's consideration will include "the rights and wishes of Yulia Skripal."

British officials say she is recovering in the hospital while her 66-year-old father remains in critical condition.

The Russian Embassy in London called her recovery "good news" and said Russian diplomats had a right to see her under the 1968 Consular Convention.

The Russian Foreign Ministry on Saturday also issued lists of questions it wants Britain and France to answer in the case, including to what extent French investigators have been involved in probing the poisoning and why.

Russia contends that Britain is exploiting "Russophobia" to undermine Moscow. On Saturday, its London embassy issued a statement warning Russians travelling to the U.K. that they could be subject to "provocations" including having various items planted in their luggage.

In another illustration of the deteriorating relations, the Russian Embassy in Britain complained about the alleged search of a Russian airliner at London's Heathrow Airport.

The embassy said British Border Forces and Customs officers searched an Aeroflot flight from Moscow on Friday in violation of international rules. the embassy called it "another blatant provocation by the British authorities."

British officials responded Saturday that it's routine to search some incoming flights. Russia has sent a diplomatic note demanding an explanation of the search, which delayed the flight to Moscow.

Katz reported from London. Lynn Berry in Washington and Irina Titova in St. Petersburg contributed.