Deadly clashes break out in Venezuela's border towns as opposition tries to bring in aid
Troops fire tear gas at crowds trying to break through government blockades
At least one aid truck goes up in flames on the Colombia-Venezuela border
Self-declared interim President Juan Guaidó urges the military to allow aid in
President Nicolás Maduro warns this would open the way for US military intervention
Several members of Venezuela's security forces have defected
Image source, ReutersThe BBC's Katy Watson in Caracas says the crisis is a huge political issue.
As lorries laden with aid are due to set off from both Colombia and Brazil and attempt to cross the border, the day will not only test the loyalty of the country's armed forces towards President Maduro, she says, but determine his future.
Several soldiers from the Venezuelan national guard have left their posts ahead of the planned aid deliveries.
Self-declared interim President Juan Guaidó says they are not "deserters" because they have decided to "stand on the side of the people and the constitution".
He adds that "the advent of freedom and democracy to Venezuela is already unstoppable".
Allow Twitter content?
This article contains content provided by Twitter. We ask for your permission before anything is loaded, as they may be using cookies and other technologies. You may want to read Twitter’s cookie policy, external and privacy policy, external before accepting. To view this content choose ‘accept and continue’.
We are at a flashpoint in the Venezuelan crisis, with tensions rising in recent days over a row about the delivery of humanitarian aid to the country.
As Venezuela faces a power struggle between President Nicolás Maduro and Juan Guaidó, who has been recognised as the country's interim leader by dozens of countries, including the US and most Latin American nations, civilians are face an economic crisis.
The country's inflation rate has seen prices soar, leaving many Venezuelans struggling to afford basic items such as food, toiletries and medicine.
Mr Guaidó says this has left thousands of others at risk of dying and about 2.7 million people have fled the country since 2015.
But President Maduro says the US is trying to manufacture a humanitarian crisis, warning that attempts to deliver aid would open the way for US military intervention.
Read more here: All you need to know about the crisis in nine charts
Clashes at the Venezuela-Colombia border