Britain has begun supplying Ukraine with new light anti-tank weapons in response to “the increasingly threatening behaviour from Russia”, the defence secretary, Ben Wallace, has announced.

The ratcheting up of military support comes as the Kremlin continues to increase its troop deployment by moving forces into Belarus, which borders Ukraine to the north, and is considered the most likely route for any invasion.

“We have taken the decision to supply Ukraine with light anti-armour defensive weapons systems,” Wallace told the Commons on Monday, adding that “a small number” of British troops would provide training to help Kyiv’s forces in using them.

The defence secretary insisted the arms sales were intended to be defensive, although the Russian president, Vladimir Putin, has recently complained about other Nato members selling modern weapons to Ukraine.

After Turkey sold TB2 anti-tank drones to Ukraine, Putin spoke to his Turkish counterpart, President Recep Tayyip Erdoğan, and according to the Kremlin, described the arms deal as provocative.

“Let me be clear: this support is for short-range and clearly defensive weapon capabilities; they are not strategic weapons and pose no threat to Russia; they are to use in self-defence,” Wallace added.

UK defence sources would not immediately spell out what weapons had been supplied and how many.

However, experts said the arms supplied were likely to be handheld next-generation light anti-tank weapons, with a range of a few hundred metres, intended to help combat Russia’s tank-heavy army.

They have similar capabilities, but are not as powerful as Javelin anti-tank missiles, supplied by the US to Ukraine from 2018. In theory, the lighter weapons can knock out a tank by striking it from above.

Labour said it supported the announcement, on which it had been briefed in advance. John Healey, the shadow defence secretary, described them as “anti-tank weapons” and said the UK must ensure they “won’t be used, unless Russia invades”.

Wallace also said he would invite his Russian counterpart, Sergei Shoigu, for bilateral talks in London, although it was far from clear whether the meeting would take place. “We are ready to discuss issues related to mutual security concerns and engage constructively, in good faith,” the British minister said.

The latest arms sale represents a step up from existing British military commitments. Until recently the UK has focused on selling ships and naval equipment to Ukraine, announcing a £1.7bn deal to supply two mine sweepers and jointly build eight ships for its small Black Sea fleet last year.

Russia has massed over 100,000 troops on its border with Ukraine, demanding that the country never become a member of Nato and insisting on other security guarantees that would amount to the creation of a sphere of influence for Moscow in former Soviet states.

Some Russian troops have begun to move into Belarus for planned military exercises, named United Resolve. But western military analysts say the most direct route for Russia to attack Kyiv is from Belarus, a manoeuvre that would circumvent the Dnieper river that runs through Ukraine’s capital.

Moscow’s demands were rejected by the west in a series of diplomatic negotiations last week, prompting concerns that Russia may be ready to consider a military options to reassert greater control over Ukraine.

Nato members have said the alliance would not intervene militarily to defend Kyiv, but have indicated that they would be prepared to hit Russia with economic sanctions – and continue to supply arms to forces inside the country both before and after any invasion.

“I have visited Ukraine five times since 2016, and I know that the Ukrainians are a proud people who will stand and fight – for their country, for democracy and for freedom,” Wallace said. “Any invasion will not be viewed as a ‘liberation’ but as occupation, and I fear that it could lead to huge loss of life on all sides.”

The German foreign minister, Annalena Baerbock, said before a meeting with her Russian counterpart on Tuesday that she hoped the tensions could be resolved by diplomacy but, if not, Moscow would pay a “high price” for aggressive acts toward Ukraine.

Tobias Ellwood, Conservative chairman of the defence committee, asked what further support Nato would provide if Putin gave the green light to an invasion. Wallace said he hoped the arms sales announced on Monday would send a message to the Kremlin.

“I hope – because I think President Putin has still not made a final decision – but I hope that that is enough to ward the Kremlin off, a united front on sanctions, which is what we are developing, prepared and ready if something were to happen, a strong resilience in Ukraine should at the very least give people a pause for thought. The first systems were delivered today in country,” he said.