Index: flang/lib/Semantics/check-omp-structure.h
===================================================================
--- flang/lib/Semantics/check-omp-structure.h
+++ flang/lib/Semantics/check-omp-structure.h
@@ -166,7 +166,7 @@
 private:
   bool HasInvalidWorksharingNesting(
       const parser::CharBlock &, const OmpDirectiveSet &);
-
+  bool IsCloselyNestedRegion(const OmpDirectiveSet &set);
   // specific clause related
   bool ScheduleModifierHasType(const parser::OmpScheduleClause &,
       const parser::OmpScheduleModifierType::ModType &);
Index: flang/lib/Semantics/check-omp-structure.cpp
===================================================================
--- flang/lib/Semantics/check-omp-structure.cpp
+++ flang/lib/Semantics/check-omp-structure.cpp
@@ -127,11 +127,52 @@
   std::map<std::string, std::int64_t> labelNamesandLevels_;
 };
 
+bool OmpStructureChecker::IsCloselyNestedRegion(const OmpDirectiveSet &set) {
+  // Definition of close nesting:
+  //
+  // `A region nested inside another region with no parallel region nested
+  // between them`
+  //
+  // Examples:
+  //   non-parallel construct 1
+  //    non-parallel construct 2
+  //      parallel construct
+  //        construct 3
+  // In the above example, construct 3 is NOT closely nested inside construct 1
+  // or 2
+  //
+  //   non-parallel construct 1
+  //    non-parallel construct 2
+  //        construct 3
+  // In the above example, construct 3 is closely nested inside BOTH construct 1
+  // and 2
+  //
+  // Algorithm:
+  // Starting from the parent context, Check in a bottom-up fashion, each level
+  // of the context stack. If we have a match for one of the (supplied)
+  // violating directives, `close nesting` is satisfied. If no match is there in
+  // the entire stack, `close nesting` is not satisfied. If at any level, a
+  // `parallel` region is found, `close nesting` is not satisfied.
+
+  if (CurrentDirectiveIsNested()) {
+    int index = dirContext_.size() - 2;
+    while (index != -1) {
+      if (set.test(dirContext_[index].directive)) {
+        return true;
+      } else if (llvm::omp::parallelSet.test(dirContext_[index].directive)) {
+        return false;
+      }
+      index--;
+    }
+  }
+  return false;
+}
+
 bool OmpStructureChecker::HasInvalidWorksharingNesting(
     const parser::CharBlock &source, const OmpDirectiveSet &set) {
   // set contains all the invalid closely nested directives
   // for the given directive (`source` here)
-  if (CurrentDirectiveIsNested() && set.test(GetContextParent().directive)) {
+  if (IsCloselyNestedRegion(set)) {
     context_.Say(source,
         "A worksharing region may not be closely nested inside a "
         "worksharing, explicit task, taskloop, critical, ordered, atomic, or "
Index: flang/test/Semantics/omp-do05.f90
===================================================================
--- flang/test/Semantics/omp-do05.f90
+++ flang/test/Semantics/omp-do05.f90
@@ -6,7 +6,7 @@
 program omp_do
 
   integer n
-  integer i,j
+  integer i,j,k
   !$omp do
   do i=1,10
     !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
@@ -18,6 +18,65 @@
   end do
   !$omp end do
 
+  !$omp do
+  do i=1,10
+    !$omp task
+    do j=1,10
+      !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+      !$omp single
+      do k=1,10
+        print *,"hello"
+      end do
+      !$omp end single
+    end do
+    !$omp end task
+  end do
+  !$omp end do
+
+  !$omp do
+  do i=1,10
+    !$omp parallel
+    do j=1,10
+      !$omp single
+      do k=1,10
+        print *,"hello"
+      end do
+      !$omp end single
+    end do
+    !$omp end parallel
+  end do
+  !$omp end do
+
+!$omp do
+do i=1,10
+  !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+  !$omp single
+  do j=1,10
+    !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+    !$omp single
+    do k=1,10
+      print *,"hello"
+    end do
+    !$omp end single
+  end do
+  !$omp end single
+
+  !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+  !$omp single
+    do k=1,10
+      print *,"hello"
+    end do
+  !$omp end single
+
+  !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+  !$omp do
+    do k=1,10
+      print *,"hello"
+    end do
+  !$omp end do
+end do
+!$omp end do
+
   !$omp parallel default(shared)
   !$omp do
   do i = 1, n
@@ -29,4 +88,19 @@
   !$omp end do
   !$omp end parallel
 
+  !$omp parallel default(shared)
+  !$omp do
+  do i = 1, n
+    !$omp task
+    do j=1,10
+      !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+      !$omp single
+      call work(i, 1)
+      !$omp end single
+    end do
+    !$omp end task
+  end do
+  !$omp end do
+  !$omp end parallel
+
 end program omp_do
Index: flang/test/Semantics/omp-nested01.f90
===================================================================
--- flang/test/Semantics/omp-nested01.f90
+++ flang/test/Semantics/omp-nested01.f90
@@ -11,4 +11,30 @@
         a = 3.14
      enddo
   enddo
+
+  !$omp do
+  do i = 1, N
+   !$omp target
+   do k = 1,N
+     !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+     !$omp do
+     do j = 1, N
+        a = 3.14
+     enddo
+   enddo
+   !$omp end target
+  enddo
+  
+
+  !$omp do
+  do i = 1, N
+   !$omp parallel
+   do k = 1,N
+     !$omp do
+     do j = 1, N
+        a = 3.14
+     enddo
+   enddo
+   !$omp end parallel
+  enddo
 end
Index: flang/test/Semantics/omp-reduction07.f90
===================================================================
--- flang/test/Semantics/omp-reduction07.f90
+++ flang/test/Semantics/omp-reduction07.f90
@@ -54,6 +54,19 @@
   !$omp end do
 !$omp end sections
 
+!$omp sections private(k)
+  !$omp target
+  do j = 1,10
+    !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+    !$omp do reduction(+:k) reduction(max:j)
+    do i = 1, 10
+      k = k + 1
+    end do
+    !$omp end do
+  end do
+  !$omp end target
+!$omp end sections
+
 !$omp parallel reduction(+:a)
 !ERROR: REDUCTION variable 'a' is REDUCTION in outer context must be shared in the parallel regions to which any of the worksharing regions arising from the worksharing construct bind.
 !$omp sections reduction(-:a)